Narrow band UVB phototherapy or systemic PUVA therapy are known treatment modalities for generalized disease. The lamps used in phototherapy contain a phosphor that emits only UVB ultraviolet light. Treatments for psoriasis include topical agents, phototherapy, and systemic agents. For psoriasis, UVB phototherapy has been shown to be effective. Artificial UV light sources from tanning units and phototherapy treatment units can also trigger PLE. Other treatment options may include steroid creams or phototherapy to darken the light patches. Other options may include salicylic acid, coal tar, benzoyl peroxide, and phototherapy. Eye protection is usually given during phototherapy treatments. Treatments may include more frequent feeding, phototherapy, or exchange transfusions. Using tanning beds allows patients to access UV exposure when dermatologist-provided phototherapy is not available. In the case of solar urticaria, phototherapy and photochemotherapy are the two major desensitization treatments. Another treatment option is a supervised course of low dose phototherapy, usually undertaken in winter. Clofibrate may decrease the duration of phototherapy. This center is equipped with photopheresis, hydrotherapy and phototherapy units. The Faroese physician Niels Finsen is believed to be the father of modern phototherapy.