Herbal Therapy in Dermatology FREE

Herbal medicine dates back thousands of years. It originated in India and China and it is still widely used in Asia. In India, Ayurvedic medicine dates back to 3000 BC. Ayurvedic medicine combines physiological and holistic principles. It is based on the concept that the human body is composed of 5 energy elements that also make up the universe: earth, water, fire, air, and space. Interaction of these elements gives rise to the 3 doshas (forces), 7 dhatus (tissues), and 3 malas (waste products). All diseases are attributed to an imbalance between the 3 doshas. Diagnosis is made by an elaborate system of examination of the physical findings, the pulse, and the urine, as well as an 8-fold detailed examination to evaluate both the physical and mental aspects of the condition. Treatment is then individually tailored to the findings.¹

Chinese medicine dates back about 4000 years and is aimed at treating the whole person. It is based on the complementary forces yin and yang. In healthy individuals, the yin and yang are in balance, and illness occurs when there is inequality between the forces. The Chinese evaluate the exchange between the environment and the body, such as food, drink, and air into the body and waste leaving the body. Special attention is placed on the physical examination of the tongue, iris, and pulse of the individual to determine the cause of the imbalance and then to determine the appropriate individual treatment. Treatment is usually a mixture of herbs, massage, and acupuncture.²

In Western medicine, herbal therapy began as folk medicine. In the United States, it began in the colonial days, when homemade botanicals were provided by the women in the home.³ Native American use of botanical treatments also greatly influenced the use of herbal therapy in the United States. In the 19th century, these traditions were expanded and used by a group of physicians known as the Eclectics. As herbal medicine has developed in the United States, it has also been influenced by European and Chinese practices.⁴

Herbal therapy has recently become increasingly popular among patients seeking alternative treatment options. The number of visits to alternative medicine practitioners in the United States is growing rapidly. In 1997, the number of visits was estimated to be 629 million, which exceeded the number of visits to all primary care physicians.⁵ Approximately $27 billion was spent out of pocket for these alternative therapies in 1997, and $3.24 billion of this was spent on herbal therapy.⁶ It is estimated that about 50% of the population uses some form of alternative medicine, and many patients do not share this information with their physicians. In a previous survey, those most likely to use unconventional treatment modalities were nonblack, college educated, and between the ages of 25 and 49 years and had an annual income greater than $35 000.⁷ Most patients seeking the alternatives do so because conventional therapy has failed or they feel there are fewer side effects, as the products are natural. This recent increase in alternative medicine has led to more research and education on the subject to enable physicians to better inform and care for their patients.

In the United States, herbal remedies are sold as dietary supplements, and standards of potency and efficacy are not currently required. In Germany, a regulatory authority known as Commission E has performed an extensive review of common botanicals. The commission has evaluated the quality of evidence, clinical efficacy, and uses of 300 herbal preparations.^8- 9 This evaluation has led to standardization of herbal treatments. Several herbal therapies for dermatologic conditions have stood the test of time for their efficacy and some show significant scientific evidence of usefulness. In this day of advanced communication between physicians worldwide, it is important that we share information on herbal therapy, effects, and interactions, so that we may offer alternatives to our patients.

Tannins have been used topically to treat acne because of their natural astringent properties. Witch hazel (Hamamelis virginiana) bark extract is commonly used by making a decoction from 5 to 10 g of herb in 1 cup (0.24 L) of water. Witch hazel is considered very safe to use topically.¹⁰ Other similar astringents can be made from white oak tree or the English walnut tree. These preparations should be strained before use and can be used 2 or 3 times per day. Commercially available preparations are not recommended, as the tannins are lost in the distillation process.¹¹

Fruit acids, such as citric, gluconic, gluconolactone, glycolic, malic, and tartaric acids, have been used topically and have shown promise in treating acne because of their exfoliative properties. In one study, gluconolactone was as effective in clearing inflamed and noninflamed acne lesions as 5% benzoyl peroxide and more effective than placebo.¹² Irritation is the main adverse effect, especially in higher concentrations.

Tea tree oil may also play a role in topical acne treatment. It is an essential oil extracted from the leaves of Melaleuca alternifolia, a small tree indigenous to Australia. It contains approximately 100 compounds, mainly plant terpenes and their corresponding alcohols.¹³ In 1990, a study of 124 patients compared 5% tea tree oil in a water-based gel with 5% benzoyl peroxide. Although the tea tree oil did not work as quickly as benzoyl peroxide, it did show statistical improvement in the number of acne lesions at the end of 3 months. Also, there was a significantly lower incidence of adverse effects such as dryness, irritation, itching, and burning with the tea tree oil (44%) than with benzoyl peroxide (79%).¹⁰(p629) There are occasional reports of allergic contact dermatitis and of poisoning if taken internally.^14- 18 However, the degradation products of monoterpenes in the tea tree oil actually appear to be the sensitizing agents.¹⁹ Therefore, topical treatment is considered very safe.

Vitex (Vitex agnus-castus) taken orally has been shown to be effective in treating premenstrual acne. The whole-fruit extract is thought to act on follicle-stimulating hormone and luteinizing hormone levels in the pituitary to increase progesterone levels and reduce estrogen levels. The German Commission E monographs recommend 40 mg/d. The main adverse effects reported are gastrointestinal tract upset and rash. It should not be taken by pregnant or nursing women.²⁰(p176) The German Commission E has also approved topical bittersweet nightshade (Solanum dulcamara) and orally administered brewer's yeast (Saccharomyces cerevisiae) for the treatment of acne because of their antimicrobial effects.²⁰(p88,118) In China, topical duckweed (Lemma minor) is used to treat acne.²⁰(p258)

Aloe vera leaves produce 2 substances, a gel and a juice or latex. The gel is obtained from the inner part of the leaf and has been used topically for centuries for the treatment of wounds and burns. The juice or latex refers to a bitter yellow fluid extracted from the specialized areas of the inner leaf skin and is generally sold as a powder that has very potent laxative effects.¹⁰(p31)

Several case reports and animal studies have demonstrated that aloe vera reduces burning, itching, and scarring associated with radiation dermatitis.²¹ It has also been shown to accelerate healing of chronic leg ulcers, surgically induced wounds, and frostbite. The mechanism of action has been studied by in vivo animal studies. Aloe vera decreases thromboxane A₂, thromboxane B₂, and prostaglandin 2α, which cause vasoconstriction and platelet aggregation. This is thought to increase dermal perfusion, reducing the risk of tissue loss from ischemia.²¹ In vitro studies have shown a carboxypeptidase that inactivates bradykinin (potent pain-inducing agent at sites of acute inflammation), thereby possibly decreasing pain at the treatment site.²² Salicylic acid has been shown to be present in aloe vera; it acts as an analgesic and anti-inflammatory by inhibiting prostaglandin production.²³ Magnesium lactate is also present in aloe vera. It is thought to act as an antipruritic by inhibiting histidine decarboxylase, which controls the conversion of histidine to histamine in mast cells.²¹ Relief of inflammation is also thought to be due to the immunomodulatory properties of the gel polysaccharides, especially the acetylated mannans.²⁴ Aloe vera has also shown bactericidal and antifungal activity in vitro. The main adverse effect of topical aloe vera gel is allergic contact dermatitis. There have also been reports of delayed healing after laparotomy or cesarean section. Taken orally, aloe vera is considered very safe when used properly.²⁵(p7)

Honey has been used topically for centuries to accelerate wound healing. It has been reported to be helpful in treating burns, decubitus ulcers, and infected wounds.²⁶ In vitro it has been shown to have antibacterial and antifungal activity to organisms commonly infecting surgical wounds.²⁷ In 1998, a small study was performed of 9 infants with large, open, culture-positive postoperative wound infections in which standard treatment (>14 days of appropriate intravenous antibiotics and cleansing with chlorhexidine) failed. These wounds were then treated with 5 to 10 mL of fresh unprocessed honey twice a day. By day 5, there was marked clinical improvement, and by day 21, the wounds were all closed, clean, and sterile.²⁸ In another randomized controlled trial, honey-impregnated gauze was compared with a polyurethane film (OpSite; Smith & Nephew, North Humberside, England) for partial-thickness burns. The honey-treated wounds healed statistically earlier (mean, 10.8 days vs 15.3 days) and with equal complications such as infection, overgranulation, and contracture compared with the polyurethane film–treated wounds.²⁹ The wound-healing properties of honey are thought to result from the debriding properties of the enzyme catalase, absorption of edema because of honey's hygroscopic properties, its ability to promote granulation and reepithelialization from the wound edges, and its antimicrobial properties.³⁰ Although there have been reports of contact dermatitis to honey, there have been no reports of significant adverse effects.³⁰

Calendula officionalis, more commonly known as marigold, has been used topically since ancient times and is currently approved by the German commission as an antiseptic and to heal wounds.⁹(p119) Contemporary herbalists continue to recommend a topical preparation for the treatment of wounds, ulcers, burns, boils, rashes, chapped hands, herpes zoster, and varicose veins. Gargles are also popular for mouth and throat inflammation.¹⁰(p129) It is widely accepted as a topical treatment for diaper dermatitis or other mild skin inflammation.³¹ This is treated with an application several times a day of an ointment or cream made by mixing 2 to 5 g of the flower heads with 100 g of ointment. A gargle or lotion can also be used, which is made by mixing 1 to 2 tsp (5-10 mL) of tincture with 0.25 to 0.5 L of water.¹⁰(p130) The main adverse effect is allergic contact dermatitis. No serious adverse effects have been reported, and it is considered safe to use both topically and orally.²⁵(p22)

The anti-inflammatory effects of marigold are thought to be due to the triterpenoids. In animal studies Calendula appears to stimulate granulation and increase glycoproteins and collagen at wound sites.³¹ It also shows in vitro antimicrobial and immune-modulating properties.¹⁰(p130)

There are also many herbs containing tannins that act as astringents, thereby helping to dry oozing and bleeding wounds. Some of the more commonly reported tannin-containing herbs that may be helpful for the topical treatment of wounds include English walnut leaf, goldenrod, Labrador tea, lavender, mullein, oak bark, rhatany, Chinese rhubarb, St John's wort, and yellow dock.¹⁰(p709)

Balm (Melissa officinalis) is a lemon-scented member of the mint family. The leaves can be steam distilled to produce an essential oil. Topical uses include treating herpes simplex and minor wounds. In a randomized double-blind trial of 116 patients with herpes lesions, 96% had complete clearing of lesions at day 8 after using 1% balm extract cream 5 times a day.³² In another trial, balm extract was placed on lesions within 72 hours of onset of symptoms. The size of the lesions and healing time were statistically better in the group treated with balm.³¹ A tannin and polyphenols appear to be responsible for its antiviral effect.¹⁰(p58) Balm appears very safe to use both topically and orally.¹⁰(p58),²⁵(p75) Other herbal preparations have also shown test tube activity against herpes simplex, but clinical studies have not yet been performed. These include Echinacea, sweet marjoram, peppermint, and propolis.¹⁰(p702)

Herpes zoster and postherpetic neuralgia have been treated with a topical licorice (Glycyrrhiza glabra, Glycyrrhiza uralensis) gel preparation.³³(p155-156) Glycyrrhizen, one of the active components of licorice, has been shown to inhibit replication of varicella zoster.³⁴ However, there have been no clinical studies to support this. Topical use appears very safe, but care should be used when it is taken orally.²⁵(p58) In China, herpes zoster is commonly treated topically with hibiscus (Hibiscus sabdariffa).²⁰(p394) This has been shown to be very safe topically and orally.²⁵(p61)

Tea tree oil (see the "Acne" section for a description) has been widely used topically for the treatment of bacterial and fungal infections. Tea tree oil has shown in vitro activity against a wide variety of microorganisms, including Propionibacterium acnes, Staphylococcus aureus, Escherichia coli, Candida albicans, Trichophyton mentagrophytes, and Trichophyton rubrum.^35- 36 In a randomized double-blind trial of 104 patients, 10% tea tree oil cream was compared with 1% tolnaftate cream and placebo cream. Symptomatic relief was comparable in the tea tree oil and the tolnaftate groups; however, there was significantly greater mycologic cure in the tolnaftate group (85%) than the tea tree oil group (30%). Cure rates between the tea tree oil and placebo groups were not statistically different.³⁷ Another randomized double-blind study of 117 patients compared a solution of 100% tea tree oil with 1% clotrimazole solution in the treatment of onychomycosis. After 6 months of treatment, the 2 groups showed comparable results on the basis of mycologic cure (11% for clotrimazole and 18% for tea tree oil) and clinical assessment and subjective rating of appearance and symptoms (61% for clotrimazole and 60% for tea tree oil).³⁸ Therefore, tea tree oil may have a role in at least symptomatic treatment of tinea pedis and onychomycosis and other superficial wounds. However, it should not be used for burns because of its cytolytic effect on epithelial cells and fibroblasts.³⁹

Garlic (Allium sativum) contains ajoene, which has been shown to have antifungal activity. In a study of 34 patients treated with 0.4% ajoene cream topically once a day for tinea pedis, 79% noted clearing within 7 days and the remainder had clearing within 14 days. At a 3-month follow-up, all participants remained free of fungus.⁴⁰ There are reports of contact dermatitis with frequent topical exposure.²⁰(p328) Oral administration should be avoided while breastfeeding.²⁵(p6) There are also reports of prolonged bleeding when garlic is taken orally.²⁰(p328)

Certain other common dermatologic infections have been treated for centuries with herbal preparations. Anise (Pimpinella anisum) seeds are a source of an essential oil that has displayed antibacterial and insecticidal activity in vitro and has been used topically to treat scabies and head lice. It should not be used in pregnancy.²⁵(p86) Neem (Azadirachta indica) is indigenous to India, and every part of the plant has been used medicinally. In a report of more than 800 villagers in India, a paste of neem and turmeric applied topically appeared to treat chronic ulcers and scabies.¹⁰(p452) It appears safe in adults, but it can be poisonous to children.¹⁰(p453) Numerous other herbs have been used for centuries in India and China to treat scabies.²⁰

There are also herbal preparations for the topical treatment of condyloma and verruca vulgaris. Podophyllin, used to treat condyloma acuminata, comes from the root of the American mayapple (Podophyllum peltatum).²⁰(p510) It should not be used during pregnancy.²⁵(p89) The German commission has approved bittersweet nightshade (S dulcamara) and oat straw (Avena sativa) for the treatment of common warts.²⁰(p88,552) Calotropis (Calotropis procera) is used in India and greater celandine (Chelidonium majus) is used in China for the treatment of warts.²⁰(p142,170) Bittersweet nightshade and celandine should also be avoided in pregnancy and while breastfeeding.²⁰(p88,170)

Traditional Chinese herbal medicine (CHM) for the treatment of atopic dermatitis and psoriasis has recently received much attention. In traditional Chinese medicine, the body is treated as a whole and the aim of therapy is to restore harmony to the functions of the body.⁴¹ This requires a mixture of various herbs individually formulated for the patient,⁴² making randomized controlled trials difficult to undertake. Recently, 2 randomized placebo-controlled crossover trials were performed in England to study the effects of orally administered CHM in the treatment of atopic dermatitis in which traditional Western therapy had failed.^42- 44 The investigators were aided by a Chinese physician who was able to create a standardized mixture of 10 herbs useful in treating atopic dermatitis characterized by erythema, lichenification, and plaques of dermatitis in the absence of active exudation or clinical infection. The 10 herbs used were Potentilla chinensis, Tribulus terrestris, Rehmannia glutinosa, Lophatherum gracile, Clematis armandii, Ledebouriella saseloides, Dictamnus dasycarpus, Paeonia lactiflora, Schizonepeta tenuifolia, and G glabra.⁴³ These herbs were placed in sachets and boiled to make a decoction that was orally administered daily as a tea. The placebo arm consisted of a decoction made from several herbs with similar smells and tastes that have no known efficacy in the treatment of atopic dermatitis. The first study focused on 37 children and showed a median decrease in erythema score of 51.0% in the treatment group compared with only a 6.1% improvement in the placebo group. The percentage surface involvement also decreased by 63.1% and 6.2% for the treatment and placebo groups, respectively. In this initial study, no serious adverse effects were found. These 37 children were offered continued treatment with the CHM and then followed up for 1 year.⁴⁵ Eighteen children completed the year of treatment and showed 90% reduction in eczema activity scores. The children who withdrew from the study did so because of lack of further response to treatment, unpalatability of the tea, or difficulty in preparation of the treatment. By the end of 1 year, 7 patients were able to discontinue therapy without relapse. Asymptomatic elevation of aspartate aminotransferase level was noted in 2 patients, which returned to normal with discontinuing treatment. No other serious sequelae were observed. In the other study, the design was similar; however, the investigators studied 31 adult patients with atopic dermatitis.⁴² Again, the decrease in erythema and surface damage was statistically superior in the treatment group compared with the placebo group. There was also subjective improvement in itching and sleep. These patients were also followed up for a year, with continued improvement and no serious adverse effects, whereas the patients who discontinued treatment noted a decline in their condition.⁴⁵ Although the sample sizes were limited during the course of the study, initial results were promising for patients in whom standard therapy failed. The main limitation appeared to be the taste and the preparation of the decoction. It should be emphasized, however, that, although no serious adverse effects were noted in this study, careful monitoring of complete blood cell count and liver function is recommended, as reports of liver failure and even death have been reported when baseline laboratory values were not followed up.^46- 48

It is known that specific herbs used in these studies have anti-inflammatory, antibacterial, antifungal, antihistaminic, immunosuppressant, and corticosteroidlike effects. A few ingredients also are smooth muscle relaxants and inhibit platelet activating factor. Several studies have tried to elucidate the mechanism of action of this group of 10 herbs (Zemophyte; Phytotech Limited, Godmanchester, England) in treating atopic dermatitis. It is known that patients with atopic dermatitis have elevated levels of the low-affinity IgE receptor CD23 expressed on circulating monocytes. In studies of interleukin (IL) 4–induced CD23 expression on monocytes, there appeared to be a reduction of the CD23 expression when the cells were exposed to the aqueous herb extracts.^2,49 Another study examined immunologic markers for T cells, macrophages, Langerhans cells, and low-affinity and high-affinity IgE receptors in biopsy specimens of lesional skin treated with Zemophyte compared with biopsy specimens of nonlesional skin.⁵⁰ The investigators found clinical improvement similar to that seen in the studies described above and also found that the improvement was associated with statistically significant reduction in CD23 antigen–presenting cells.

In a survey of patients with psoriasis at a large university dermatology practice, 51% of patients used 1 or more alternative therapeutic modalities.⁵¹ This is compatible with previous Norwegian surveys of patients with psoriasis.⁵² Herbal therapy is one of the most frequently chosen alternative therapies. Psoriasis has been treated for centuries with herbal preparations, both topical and oral. There are many herbal preparations composed of furocoumarins, which act as psoralens when combined with UV-A. One common CHM, known as Radix Angelicae dahuricae, contains the furocoumarins imperatorin, isoimpertorin, and alloimperatorin. In a study involving 300 patients with psoriasis, this CHM, taken orally, was combined with UV-A therapy and compared with standard treatment of psoralen–UV-A with methoxsalen. The efficacy of the 2 treatments was equivalent; however, there were fewer adverse effects such as nausea and dizziness in the group treated with the CHM and UV-A.⁴⁶ There are also topical preparations made from herbs that have shown systemic efficacy against psoriasis, but are too toxic when given systemically.⁵³ One example is the topical CHM composed of the plant Camptotheca acuminata decne. An open trial including 92 patients with psoriasis found that this CHM was statistically more effective than 1% hydrocortisone. However, allergic contact dermatitis was seen in 9% to 15% of the patients in the CHM group. Several other studies have compared various Chinese herbal preparations with ethyliminum, which is a popular "Western remedy" in China, although it is no longer used as standard therapy for psoriasis in Western medicine. Therefore, although results were promising, there is no applicability, since ethyliminum is no longer used or comparable with other current therapy. More double-blind placebo-controlled trials are needed to compare these herbal preparations with current standard Western treatment. However, this is difficult, because the mixture of herbs prescribed varies individually depending on the subtype of psoriasis ("blood-heat" type, "blood deficiency dryness" type, and "blood stasis" type), which is determined in traditional Chinese medicine by many findings, including the lesions of psoriasis, the pulse, and the condition of the tongue.⁴⁶

As previously described, aloe vera has been used for centuries for wound healing and has recently been shown to be a potential treatment for psoriasis. In a double-blind placebo-controlled study, 60 patients with slight to moderate plaque psoriasis were treated topically with either 0.5% hydrophilic aloe cream or placebo. The aloe-treated group showed statistically significant improvement (83.3%) compared with placebo (6.6%). There were no adverse effects in the treatment group.⁵⁴

The main ingredient in cayenne pepper, Capiscum frutescens or capsaicin, has also been studied for the treatment of psoriasis. Two trials have shown that 0.025% cream used topically is effective in treating psoriasis. The first study showed significant decrease in scaling and erythema during a 6-week period in 44 patients with moderate and severe psoriasis.⁵⁵ The second was a double-blind study of 197 patients with psoriasis treated with the cream 4 times daily for 6 weeks. It showed a significant decrease in scaling, thickness, erythema, and pruritus.⁵⁶ The main adverse effect reported was a short-lived burning sensation at the application site. Capsaicin is contraindicated on injured skin or near the eyes, and Commission E suggests it not be used for more than 2 consecutive days, with a 14-day lapse between applications.²⁵(p23)

In Europe, especially Germany, there is much attention to the use of topical herbal preparations as corticosteroid-sparing agents for the treatment of skin inflammation, including dermatitis and psoriasis. Several herbs are currently approved by Commission E for topical treatment of skin inflammation. These include the following botanicals: Arnica (Arnica montana), German chamomile (Matricaria recutita), bittersweet nightshade (S dulcamara), and brewer's yeast (S cerevisia) are thought to have anti-inflammatory and antibacterial effects. Heartseases (Viola tricolor), English plantain (Plantago lanceolata), fenugreek (Trigonella foenum-gaecum), and flax (Linum usitatissimum) contain mucilages, which act as emollients and soothe. Agrimony (Agrimonia eupatoria), jambolan bark (Syzygium cumini), oak (Quercus rubar), walnut (Juglans regia), and St John's wort (Hypericum montana) contain tannins and act as astringents. Oat straw (A sativa) is also approved for its soothing and antipuritic qualities.^8- 10,20

Arnica comes from the dried flowers of A montana or other arnica species. Although oral administration can cause severe health hazards in even small amounts, the external preparations appear to be very safe and effective. Arnica has been used for centuries as an anti-inflammatory aid to rub into sore muscles and joints, bruises, insect bites, boils, inflamed gums, acne eruptions, and hemorrhoids. It is also an ingredient found in many seborrheic dermatitis and psoriasis preparations. When used as a compress, 1 tbsp (15 mL) of tincture is mixed with 0.5 L of water; if used as an infusion, 2 g of dried arnica is mixed with 100 mL of water. The cream or ointment preparations should contain a maximum of 15% arnica oil or 20% to 25% tincture.⁹(p85),¹⁰(p45)

It has been known since the 1980s that the active ingredients of arnica are the sesquiterpene lactones such as helanalin, 11α,13-dihydrohelenalin, chamissonolid, and their ester derivatives. It appears that these components act to reduce inflammation by inhibiting the transcription factor nuclear factor–κB. Nuclear factor–κB controls the transcription of many genes, including cytokines such as IL-1, IL-2, IL-6, IL-8, and tumor necrosis factor α, as well as adhesion molecules intercellular adhesion molecule 1, vascular cellular adhesion molecule 1, and endothelial leukocyte adhesion molecule 1. It also inhibits many genes responsible for antigen presentation and for cyclo-oxygenase II.⁵⁷

Although most individuals tolerate the external preparations well, there have been many reports of contact dermatitis. There are also several reports of irritation when arnica is used at stronger concentrations or for longer periods than are recommended. It is not recommended to use it on open wounds or broken skin.²⁵(p14) Also, it is important to buy arnica from a reputable source, as it is a protected species in some countries and other plants have been surreptitiously used.

German chamomile (M recutita), a member of the daisy family, has been used for centuries, internally and externally, for almost all ailments, most notably gastrointestinal tract symptoms, oral or skin inflammation, and dermatitis. A tea is made by using 2 to 3 tsp (10-15 mL) of dried flowers per cup of water and is taken internally or used as a compress. Other topical preparations with cream or ointment bases have also been used and studied in Germany.⁹(p324) Studies have shown that topical chamomile is comparable with 0.25% hydrocortisone and showed improvement in a sodium lauryl sulfate–induced contact dermatitis.³¹ One small double-blind trial found that chamomile significantly decreased the surface area of wounds, and, in animal studies, healing time was reduced with chamomile. It has also shown in vitro antimicrobial activities.¹⁰(p157) The main adverse effect reported is allergic contact dermatitis, and it is considered safe to use topically and orally.²⁵(p74)

The anti-inflammatory, wound-healing, and antimicrobial effects of German chamomile are attributed to a blue essential oil that contains sesquiterpene alcohol, α-bisabolol, chamazulene, and flavinoids. These components have shown anti-inflammatory and antispasmodic properties in animal studies. This is partially attributed to the inhibition of cyclo-oxygenase and lipoxygenase in vitro. The flavinoids also act by inhibiting histamine release from antigen-stimulated human basophilic polymorphonuclear leukocytes.³¹ Bisabolol has also been shown to promote granulation tissue in wound healing.¹⁰(p157)

Several herbs contain a substance called mucilage, which is useful topically to soothe and act as an emollient on skin. Mucilage quickly swells into a gooey mass when it comes in contact with water, thereby aiding in dry or mildly inflamed skin. The material will also dry and can be used as an herbal bandage for minor wounds. The herbs most notable for their mucilage content are flax, fenugreek, English plantain, heartseases, marshmallow, mullein, and slippery elm.^10,20

Oats have been used topically for several hundred years for their soothing and antipruritic properties when placed in baths, and they are approved for this use by the German commission.⁹9(p97),²⁰(p552) Colloidal oatmeal turns to a gooey mass when mixed with liquid, thereby coating the skin and sealing in moisture. This soothing and moisturizing property is attributed to the gluten content in the plant. This can be useful in atopic dermatitis as well as idiopathic pruritus of the elderly.

As previously mentioned, several herbs contain tannins, which act as astringents. Tannins used topically are thought to be beneficial in treating dermatitis by coagulating surface proteins of cells, thereby reducing permeability and secretion. The precipitated proteins also form a protective layer on the skin.³¹ They may also have antimicrobial properties. Several herbs are known to contain tannins. Some of the more commonly used agents for the treatment of dermatitis include witch hazel, oak bark, English walnut leaf, agrimony, jambolan bark, Labrador tea, goldenrod, lady's mantle, lavender, mullein, rhatany, Chinese rhubarb, yellow dock, and St John's wort. Although there is limited research on the use of these agents, one study showed that a witch hazel extract in a phosphatidyl choline base was less effective in reducing erythema from UV radiation and cellophane tape stripping in 24 healthy patients than 1% hydrocortisone.⁵⁸ In another clinical trial, one group with atopic dermatitis (n = 36) and another group with contact dermatitis (n = 80) compared witch hazel extract with control. In the atopic group, the witch hazel was slightly superior in reducing inflammation and itching. There are also anecdotal reports of witch hazel's usefulness in treating atopic dermatitis.³¹

Pansy flower infusion is recommended by German health authorities for the topical treatment of seborrheic dermatitis, especially in infants. The infusion is made by mixing 1 to 2 tsp of flowers per cup of water and is used as a wet dressing. Salicylic acid in concentrations of about 0.3% appears to be the active ingredient. It also contains saponins and mucilage, which have softening and soothing action. No adverse effects have been reported with its topical use.¹⁰(p480)

Jewelweed (Impatiens biflora) is reputed to be useful in topically treating poison ivy contact dermatitis. However, research results are conflicting. In a 1958 study, treatment with jewelweed was comparable with standard treatment for poison ivy contact dermatitis; in 108 of 115 patients, symptoms cleared within 2 to 3 days.⁵⁹ However, in a 1980 study, not only did jewelweed extract fail to reduce symptoms of poison ivy dermatitis, but symptoms became worse, and in a recent study there was no prophylactic effect of jewelweed in poison ivy dermatitis.^60- 61 Jewelweed has been mentioned to be most helpful if applied to the area the poison ivy touched as soon after contact as possible; however, this was not addressed in the studies. There have been no reports of topical jewelweed causing adverse effects.¹⁰(p365)

Chronic venous insufficiency (CVI) is a common condition affecting at least 10% to 15% of men and 20% to 25% of women.⁶² It is a source of great cost and morbidity. Compliance with current treatments such as compression stockings is poor, which has led to the search for alternative therapies.

Horse chestnut seed extract (HCSE) is one of the most studied herbal alternatives. Horse chestnut (Aesculus hippocastanum) contains the plant compounds known as terpenes, and the active component appears to be aescin.¹⁰(p343) The mechanism of action appears to be related to inhibiting leukocyte activation, an important physiological component of CVI. It is also thought to prevent vascular leakage by inhibiting elastase and hyaluronase, which are involved in proteoglycan degradation at the capillary endothelium.⁶³ There have been many double-blind randomized trials of oral HCSE for patients with CVI. It has been shown that HCSE decreases lower-leg volume as well as calf and ankle circumference. There were also decreased symptoms such as fatigue, tenderness, and pruritus. Another study showed relative equality of using HCSE compared with grade II compression stockings for treatment of CVI.⁶⁴ Most of these studies achieved statistically significant results for treatment of CVI with doses of HCSE containing 100 to 150 mg of aescin per day, most commonly taken as 50 mg twice a day. Adverse effects reported were minimal and included gastrointestinal tract symptoms, dizziness, headache, and pruritus. The rates of reported adverse effects were from 0.9% to 3.0% and in several studies were not statistically different from rates of adverse effects with placebo. Although there are no long-term studies of oral HCSE in treating CVI and its sequelae, these results seem promising and offer patients a safe alternative to compression stockings. In Europe, HCSE has also been used in the form of a topical gel, lotion, or ointment to reduce inflammation and discomfort associated with varicose veins, phlebitis, and hemorrhoids.¹⁰(p344)

The seeds of the horse chestnut tree are poisonous and must be specially prepared by a reputable manufacturer, such as those seeds currently on the American market, to remove all toxins. Once the toxins have been removed, it is considered relatively safe taken orally. There has been one case report of drug-induced lupus attributed to Venocuran (Knoll AG, Ludwigshafen, Germany), a drug for venous insufficiency containing HCSE.¹⁰(p344-345) There have been reports of contact dermatitis when used topically.⁹(p269)

In France there is also research on the use of herbs in CVI. Several double-blind trials have studied the effects of grapeseed extract on CVI. Grapeseed extract contains oligomeric proanthocyanidins, which are bioflavinoids shown to be beneficial in strengthening capillaries. The dosage in the studies varied from 50 mg orally once a day to 100 mg 3 times per day. No serious adverse effects have been reported.²⁰(p363-364)

Ginkgo (Ginkgo biloba) has been used orally in China for centuries and more recently in Europe and the United States for numerous conditions, including heart disease, asthma, vertigo, tinnitus, impotence, cerebral and vascular insufficiency, peripheral vascular disorders, dementia, and other conditions. Much research indicates that ginkgo promotes vasodilation, thereby improving many of the conditions above. Most of this research on ginkgo relates to cerebral insufficiency and claudication, suggesting that it may be more useful for these vascular disorders than for CVI.¹⁰(p293),⁶⁵ Care should be used when ginkgo is taken orally, as there have been reports of subarachnoid and intracerebral hemorrhage, as well as increased bleeding time.²⁰(p344)

Witch hazel (H virginiana) contains considerable amounts of tannin, making it a useful astringent. It has been used topically to soothe inflammation of the skin and mucous membranes in such disorders as varicose veins and hemorrhoids. Animal research suggests that the witch hazel extract has local styptic and vasoconstrictive effects. The alcohol fluid extract has also been shown to cause venous constriction in rabbits; thus, it is often used orally for CVI in Europe. Although it appears safe when taken orally, efficacy of such treatment has not been well studied in humans.⁸(pp670-672), ²⁵25(p59)

In addition to horse chestnut, the German commission has approved orally administered butcher's broom (Ruscus acuteatus) and sweet clover (Melilotus officinalisis) for relief of symptoms associated with venous insufficiency such as pain, heaviness, pruritus, and swelling. In animal studies, butcher's broom has been shown to increase venous tone and also has diuretic properties. Sweet clover has been shown to increase venous reflux.²⁰(p132) However, reflux is probably a misnomer, as the term is generally used to describe a backward flow, and in the case of venous return it would indicate undesired pooling. A better description of the effect of sweet clover would be to say that it increases venous return. Both butcher's broom and sweet clover appear to be safe when used as recommended.²⁰(p132), ²⁵(p100)

Few randomized trials have studied herbal remedies for alopecia. Recently, a randomized controlled double-blind study of 86 patients with alopecia areata was performed.⁶⁶ A mixture of essential oils including thyme, rosemary, lavender, and cedarwood in carrier oils; grapeseed; and jojoba (a liquid wax) was massaged into the scalp daily. The control group massaged only the carrier oils into the scalp. Success was evaluated on the basis of sequential photographs, by both a 6-point scale and a computerized analysis of areas of alopecia. Overall, the treatment group had statistically significant improvement over the control group (44% vs 15%). This improvement compares with the success of standard treatment practices used conventionally. There were no adverse effects.

Another study evaluated the topical use of a Chinese herbal formula, Dabao (Engelbert & Vialle, Venlo, the Netherlands), for the treatment of androgenic alopecia.⁶⁷ In this study, 396 patients participated in the double-blind placebo trial, which lasted 6 months. The components of Dabao include 50% ethanol, 42% water, and 8% Chinese herbal extracts, including saffron flowers, mulberry leaves, stemona root, fruits of the pepper plant, sesame leaves, the skin of the Szechuan pepper fruit, ginger root, Chinese angelica root, bark of the pseudolarix, and fruit of the hawthorn. The components of the placebo included 50% ethanol, 48% water, and 2% odor and coloring agents consisting of cherry laurel water, cinnamon water, licorice syrup, sugar syrup, and a solution of burned sugar. In both groups there was an increase in nonvellus hairs. Although the Dabao group was statistically superior to the placebo group in number of nonvellus hairs, the cosmetic improvement in both groups was minimal. Therefore, although there were no reported adverse effects, improvement is unlikely.

There has been much research on the use of teas in the prevention and treatment of skin cancer. Tea is manufactured from the leaf and bud of Camellia sinensis. The majority of tea consumed worldwide is in the form of black tea. However, in Asia, green tea is most commonly consumed, and oolong tea is popular in China. Teas contain polyphenolic compounds, which have antioxidant properties. The oxidative states of these compounds vary between the different tea formulations. Green tea is produced from the fresh leaves, and preparation is aimed at avoiding oxidation and polymerization of the polyphenols. Production of black tea involves a controlled fermentation process. Green tea has been shown in several mouse models to have anti-inflammatory and antitumorigenic properties. This is thought to be due to the polyphenolic constituent (−)-epigallocatechin-3-gallate. Numerous studies of green tea and skin cancer were recently reviewed.⁶⁸ It was found that topical application or oral consumption of green tea protects against inflammation, chemical carcinogenesis, and photocarcinogenesis. Green tea has been shown to block many mediators in the inflammatory process important in the early steps of skin tumor promotion. It also appears that there is inhibition of biochemical markers of chemical carcinogenesis, inhibition of UV-induced oxidative stress, and prevention of UV-induced immunosuppression.⁶⁸ There is also evidence that green tea protects against psoralen–UV-A–induced photochemical damage to the skin.⁶⁹ Therefore, many cosmetics and skin care products recently have been supplemented with green tea. However, more research in humans is needed to understand the true benefits.

There is also evidence that black tea may play a role in the prevention of skin tumors. It appears that the theaflavins are the active components in chemoprevention.⁷⁰ Several studies have provided evidence that topical application of constituents in black tea can decrease UV-B–induced erythema, inhibit tumor initiation, and act as an antitumor promoter.^71- 72 Oral administration of black tea also appears to inhibit tumor proliferation and promotes tumor apoptosis in nonmalignant and malignant skin tumors.⁷³ A recent survey of older patients compared tea consumption and history of squamous cell carcinoma. There was a lower risk of squamous cell carcinoma in patients who consumed hot black tea than in nonconsumers.⁷⁴ Studies comparing the effectiveness of black and green teas in protecting against UV-induced skin tumors are conflicting as to which is more beneficial.^75- 78 However, it does appear that caffeinated teas are more protective than decaffeinated teas and that caffeine alone has some inhibitory effects on UV-B–induced carcinogenesis.^76- 78

There are also a few reports of other herbs playing a role in the prevention of skin tumors in mice. Rosemary (Rosmarinus officinalis) extract has been reputed to have antioxidant activity. Recently, a methanol extract of the leaves was evaluated for its effects on skin tumors in mice. It was found that topically applied rosemary inhibited induction and promotion of skin tumors in mice treated with known chemical carcinogens. Although the exact mechanism of action is still under study, it appears that several components of the extract are important in this process. This finding suggests that it was not the antioxidant properties alone that were beneficial in the prevention of skin tumors.⁷⁹ Rosemary should not be used in pregnancy.²⁵(p99)

Propolis is a resinous material produced by honeybees from the buds and bark of certain plants and trees. It has been used for centuries for antimicrobial, anti-inflammatory, analgesic, and antitumor effects. These properties are thought to be due to the flavinoid and related phenolic acids that are components of propolis. Recently, a tumoricidal component, clerodane diterpenoid, was isolated. This compound was studied for its topical effects on skin tumorigenesis in mice. Clerodane diterpenoid appeared to reduce the incidence of chemically induced dysplastic papillomas by inhibiting the synthesis of DNA in a de novo pathway and by suppressing the growth of tumors by decreasing DNA synthesis in a salvage pathway.⁸⁰

Red ginseng is a classic traditional Chinese medicine thought to enhance immune function of the body. In a recent study, red ginseng extracts used topically appeared to inhibit chemically induced skin tumors in mice. This is thought to be due to immune-modulating properties of the red ginseng.⁸¹

Silymarin is a flavinoid isolated from milk thistle (Silybum marianum) and is approved by the German commission for liver disease because of its antioxidant properties. Recently, a study was performed to assess whether this antioxidative effect would protect against tumor promotion. Topically applied silymarin appeared to possess high protective effects against chemically induced skin tumor promotion in mice. This may involve inhibition of promoter-induced edema, hyperplasia, and proliferation as well as the oxidant state.⁸² These results are promising, yet more research involving human models is needed. Silymarin appears to be safe to use topically and orally when used appropriately.²⁵(p107)

Many patients have the misconception that, because herbs are "natural," there are no adverse effects. Physicians often do not question patients about herbal supplements, and patients are often reluctant to divulge the use of these agents for fear of criticism from their physician. It is important that dermatologists become aware of the most common, as well as the more serious, effects. This will aid in better education of patients, as well as better diagnosis of possible fatal sequelae.

Herbal therapies vary greatly in their therapeutic indexes. For example, some are consumed as foods and have high therapeutic indexes, and others are highly biologically active and must be used very carefully. Safety of the herbs mentioned in this article were addressed in each section, and further discussion of interactions of herbal therapies that may be encountered in the dermatologic setting follows.

Many cutaneous reactions to herbal preparations have been reported. The most common cutaneous adverse effect of herbal preparations is allergic contact dermatitis. However, more serious cutaneous reactions have been reported. Two patients developed erythroderma after using topical herbal treatments for psoriasis and atopic dermatitis, and 1 patient developed Stevens-Johnson syndrome after taking "Golden Health Blood Purifying Tablets," which contained multiple herbs, including red clover, burdock, queen's delight, poke root, prickly ash, sassafras bark, and Passiflora.⁸³ There have been reports of bullous and nodular lichen planus induced by ingestion of native African medicines.⁸⁴ A young woman has also been described with leukemia-related Sweet syndrome elicited by pathergy to topical arnica cream.⁸⁵

Serious systemic adverse effects have been reported with the use of CHM for the treatment of dermatologic disorders. The most common are hepatotoxic effects. Although most patients recover without serious consequences as long as the medication is stopped, there have been reports of patients with acute liver failure and death. There are also reports of renal failure and agranulocytosis.^46- 48 One patient has been described with adult respiratory distress syndrome after administration of a CHM, Kamisyoyo-san, for seborrheic dermatitis.⁸⁶ Another patient was described with reversible dilated cardiomyopathy after treatment for her atopic dermatitis with a Chinese herbal tea.⁸⁷ There are also several reports of Chinese and Indian herbal medicines containing heavy metals, such as lead, arsenic, and mercury. Prescription medications have also been found in over-the-counter herbal formulations from other countries.

There are many possible drug interactions with herbs and prescription medications. The most important in the dermatologic setting are discussed. The immune-modulating effects of Echinacea, Astragalus, licorice, alfalfa sprouts, vitamin E, and zinc may decrease the efficacy of corticosteroids and immunosuppressants.⁸⁸ There are herbs that have been shown to cause hepatitis and therefore should not be used in combination with such medications as methotrexate. These include many of the ingredients in the CHM preparations, as well as Echinacea, chaparral, germander, ragwort, and life root.^87,89 Herbs containing gamolenic acid, such as evening primrose oil, which has been used for dermatitis, psoriasis, and xerosis, lower the seizure threshold, and therefore dosages of anticonvulsants may need to be increased.⁸⁷

In addition to the adverse effects discussed already, patients should be counseled on the lack of regulation for herbal medicines. There are no quality-control measures currently in place in the United States to ensure the purity, concentration, or safety of herbal supplements. Although herb manufacturers are restricted from making efficacy statements, there are no regulations on claims for which symptoms these herbs can alleviate. In the United States, there are also no regulations on which herbs can be restricted in formulations.⁹⁰

The use of alternative medical therapy including herbs is increasing dramatically in the United States. Many of these herbal therapies have been used for centuries and show good anecdotal results. A few randomized controlled trials have also shown promising results in the use of herbal therapies for the treatment of dermatologic disorders. Other countries, such as Germany, are now requiring standardization of herbal preparations and making specific recommendations as to the use and efficacy of herbs in the treatment of disease. However, much more research is needed. For now, it is important to know what common herbal alternatives exist and which potential adverse effects can occur so as to counsel patients more effectively.

Accepted for publication July 6, 2001.

Corresponding author and reprints: Philip D. Shenefelt, MD, Division of Dermatology and Cutaneous Surgery, Box 79, Department of Internal Medicine, College of Medicine, University of South Florida, 12901 Bruce B. Downs Blvd, Tampa, FL 33612 (e-mail: pshenefe@hsc.usf.edu).