Balneophototherapy for Psoriasis Using Saltwater Baths and UV-B Irradiation, Revisited

It is well known that particular climatic conditions result in a clear improvement of skin disorders such as psoriasis vulgaris. In many medical centers, remarkable results have placed climatotherapy on the list of the most effective and safe treatment options for psoriasis. For example, over the past 30 years, tens of thousands of patients with psoriasis have successfully been treated at Israel's Dead Sea spas. Sunlight and salt water are the 2 main components of the therapy regimen at the Dead Sea. Other examples of unique and special places for climatotherapy and spa therapy are the Kangal hot spring in Turkey and the Blue Lagoon in Iceland, respectively.^{1 - 4} Because the aforementioned treatment modalities are tied to special geographic settings, balneophototherapy (BPT) was established in rehabilitation centers in Germany about 30 years ago. It represents an alternative phototherapeutic regimen that combines saltwater baths and artificial UV irradiation. This regimen has predominantly been used to treat patients with psoriasis in European countries such as Germany.⁵

However, there has been no strong evidence—regarding climatotherapy or BPT—that the combined treatment with saltwater baths and UV irradiation is superior to UV exposure alone.^{4 - 6} Although there are numerous large studies giving support to the efficacy of climatotherapy and BPT,^{7 - 9} only a few controlled studies on a limited number of patients with psoriasis have investigated the therapeutic effect of salt water baths before UV exposure.^{3 - 4 ,10} Data from these studies indicate an additional effect from the use of salt water baths before UV exposure. However, the results were put into perspective by the data from 2 other, randomized controlled trials. In 2001, a French study group¹¹ published the first randomized, controlled, observer-blinded, 3-arm trial comparing saline spa (Salies de Béarn) water baths alone, spa water baths plus narrowband (NB) UV-B therapy, and NB UV-B monotherapy in 71 patients with psoriasis. The authors concluded that spa water baths alone had a minor therapeutic effect in psoriasis, and the beneficial effect of bathing to enhance phototherapy was not demonstrated. However, the statistical power of that study could detect only large differences of at least 20% in variation of the clinical score. Dawe et al¹² conducted a randomized controlled trial on BPT comparing Dead Sea salt soaks plus NB UV-B therapy with NB UV-B monotherapy. Based on their observations, the addition of pretreatment salt soaks to NB UV-B therapy did not result in a clinically important improvement in the clearance of psoriasis. There is a wealth of evidence demonstrating that NB UV-B therapy is superior to conventional UV-B therapy.^{13 - 14} It is possible that the use of such a highly effective treatment modality will put the effect of any adjunct into perspective.

Although BPT has widely been used in Germany during the last 3 decades, the German Standing Committee of Statutory Health Insurance Physicians and Sickness Funds declined reimbursement for BPT in the beginning of 2000.⁶ Therefore, the use of BPT has dramatically decreased during the past few years. The decision of the committee was mainly based on the lack of consistent guidelines and on the absence of data from randomized controlled trials confirming the superiority of BPT over monophototherapy.^{5 - 6} Researchers from Germany recently performed 2 excellent randomized controlled trials.^{15 - 16} The first study, involving 1241 patients, convincingly demonstrated that bathing in salt water before UV-B exposure is superior to UV-B monotherapy as well as to tap water baths before UV-B exposure.¹⁵

The results of the second trial, involving 143 patients, indicated that BPT using low concentrated saline spa water baths followed by conventional UV-B therapy was superior to conventional UV-B monotherapy at the end of a 6-week treatment course.¹⁶ Moreover, Schiener et al¹⁵ showed that even tap water baths followed by UV-B irradiation result in significantly higher clearance rates compared with UV-B monotherapy. The concentration and mineral composition of the salt solution were thought to play a major role in BPT for psoriasis. However, data obtained from small comparison studies suggest that any additional benefits from soaking in salt water and tap water before BPT are unlikely to be attributable to the salinity of the liquids.^{5 ,10 ,15 ,17} Increased water uptake by the stratum corneum, followed by enhanced UV transmission and a decrease in optical reflection and scattering after bathing, could cause the biophysical mechanisms of action that may result, first, in a decrease of the minimal erythema dose and, second, in an increase of the therapeutically effective UV gain.^{18 - 19} Nevertheless, neither Schiener and colleagues¹⁵ nor Dawe and coworkers¹² observed an increase in erythemal response to UV-B or a decrease in the cumulative UV-B dose after salt water exposure. Both previous open prospective studies and recent randomized controlled trials have demonstrated that BPT is a safe and well-accepted treatment modality with no severe adverse effects.^{5 ,7 - 9 ,15 - 16}

There is no standardized treatment regimen for BPT to date.⁵ Natural spas (rehabilitation centers) as well as salt solutions of different concentrations (1% up to 30%) are used for inpatient and outpatient BPT. The main ionic component is sodium chloride. However, similar to the Dead Sea composition, some treatment modalities include a significant amount of magnesium, calcium, and sulfate. The baths, which last approximately 20 minutes at a temperature of 30°C to 35°C, usually take place in conventional bathtubs or pools. The foil bath method has the advantage of reducing the volume of the salt water bath to about 10 L.²⁰ However, the efficacy of the latter method was investigated in only 1 noncontrolled study. Generally, salt water baths are followed by UV-B irradiation. By contrast, in synchronous BPT (eg, TOMESA [German, from Totes Meer Salz, Dead Sea salt] Therapiesystem; Grünbeck Wasseraufbereitung Gmbh, Höchstädt ad Donau, Germany), the baths and UV-B irradiation are performed synchronously (Figure). The most frequently used UV regimens for BPT for psoriasis include NB, broadband, and selective UV-B radiation (Table).⁵

In conclusion, it is time for a renewed appraisal of BPT. Our confidence in the superiority of BPT over monophototherapy has significantly increased as a result of the convincing findings from the latest randomized controlled trials involving a large number of patients with psoriasis.^{15 - 16} Besides pure efficacy rates, we also have to take into account the high acceptance rates of BPT by patients with psoriasis, possibly indicating a holistic approach that includes time for relaxation as well as psychological effects that may also contribute to clearance of psoriasis.^{1 ,12} However, such a holistic approach can hardly be investigated independently, since it is very difficult to design a proper double-blind, placebo-controlled trial on BPT. Also, we must not forget the economical and practical drawbacks that are often associated with BPT.^{3 - 4} Nevertheless, in special medical settings (eg, rehabilitation centers), particularly where natural resources (eg, spas) can be used, BPT is certainly the phototherapeutic modality of the first choice for the treatment of psoriasis. To optimize the cost-effectiveness of BPT in general practice, future studies should address issues of mechanisms of action, methodology, and standardization of BPT (eg, salt concentration and mineral content) in more detail.

Correspondence: Dr Gambichler, Department of Dermatology, Ruhr-University Bochum, Gudrunstrasse 56, 44791 Bochum, Germany (t.gambichler@klinikum-bochum.de).

Financial Disclosure: None reported.

Additional Information: The photographs for the Figure were provided by Remus Vasa, MD, TOMESA Clinic, Bad Salzschlirf, Germany.