A review of studies recommends that people who are susceptible to skin cancers exercise caution when using UV light therapy as a treatment.A major mechanism of NB-UVB is the induction of DNA damage in the form of pyrimidine dimers. This type of phototherapy is useful in the treatment of psoriasis because the formation of these dimers interferes with the cell cycle and stops it. The interruption of the cell cycle induced by NB-UVB opposes the characteristic rapid division of skin cells seen in psoriasis. The activity of many types of immune cells found in the skin is also effectively suppressed by NB-UVB phototherapy treatments. The most common short-term side effect of this form of phototherapy is redness of the skin; less common side effects of NB-UVB phototherapy are itching and blistering of the treated skin, irritation of the eyes in the form of conjunctival inflammation or inflammation of the cornea, or cold sores due to reactivation of the herpes simplex virus in the skin surrounding the lips. Eye protection is usually given during phototherapy treatments.PUVA combines the oral or topical administration of psoralen with exposure to ultraviolet A (UVA) light. The mechanism of action of PUVA is unknown, but probably involves activation of psoralen by UVA light, which inhibits the abnormally rapid production of the cells in psoriatic skin. There are multiple mechanisms of action associated with PUVA, including effects on the skins immune system. PUVA is associated with nausea, headache, fatigue, burning, and itching.
A palmoplantar hyperhidrosis is excessive sweating localized to the palms of the hands and soles of the feet. It is a form of focal hyperhidrosis in that the excessive sweating is limited to a specific region of the body. As with other types of focal hyperhidrosis (e.g. axillary and craniofacial) the sweating tends to worsen during warm weather. See also
Hyperhidrosis


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