It may be difficult to find a cure for psoriasis (suh-RYE-uh-sihs) until its cause is fully understood. At present, doctors suspect that genetics, infection or injury, and autoimmune malfunction may all play a role in psoriasis. But until more is known, current treatments are limited to controlling the symptoms. Nevertheless, these treatments may allow the skin to heal and remain clear for weeks, months, or even years. The particular method chosen may depend on the type of psoriasis you have, its severity, and your overall health. Mild to moderate cases are usually treated first with topical prescription creams and ointments containing vitamin D and vitamin A derivatives, coal tar, steroids, or a substance called anthralin (ANN-thruh-lihn). Moderate to severe psoriasis may benefit from phototherapy, or ultraviolet light treatment using the UVB (U-V-B) part of the spectrum. When the condition is advanced, oral medications that suppress the immune system, like methotrexate (meth-oh-TREK-sate) and cyclosporin (sy-kloh- SPORE-ihn), may be required. Sometimes, a combination of methods may provide the best results. Most treatments for psoriasis have unwanted side effects, which must be balanced against the discomfort of the problem itself. These effects usually fade once the therapy is discontinued.