As dermatologists who are constantly faced with different types of cutaneous lesions and disorders, we find that it is not uncommon that patients ask about the possible cause or origin of these eruptions. Many patients believe that all the macules, papules, urticaria, or nodules that have appeared on their skin are due to an as-yet undiscovered allergy. In other cases, patients or their companions fear that these eruptions appear because of an internal disease, mostly a “blood disease.” Thus, once we have examined their skin thoroughly, it is not uncommon to hear from them: “Doctor, is there something wrong with my blood?” (In Spanish: “ Doctor, ¿no será que tengo algo en la sangre? ”). Luckily, most of the times we can readily reassure them that their skin is the only place where something is going wrong, for most of these eruptions are common skin diseases, such as urticaria, psoriasis, eczema, and so forth.