Most of the oral prescription medications available to the psoriasis sufferer have serious side effects and are only used in severe, persistent cases that require rapid results.

Methotrexate, a drug originally to treat cancer, has been found to interfere with the rapid cell growth associated with psoriasis. It is used only under a physician's supervision and prolonged usage requires annual or biannual liver biopsies.

Disadvantages: The side effects are liver and lung damage, fetal death and birth defects (fathers and mothers taking this medication need to cease the medication for several months prior to conception), decreased numbers of blood cells, and intestinal ulcers. Many sufferers can fail to respond after prolonged use, and the disease may then rebound with an even greater severity.

Cyclosporines, drugs developed to suppress the immune systems in transplant patients, are also showing results in treating this autoimmune disorder.

Disadvantages: The drug suppresses the immune system, can cause kidney damage and high blood pressure, and increases the risk of developing lymphomas and other types of cancer.

Tegison, a vitamin A derivative, is an oral retinoid used for difficult cases.

Disadvantages: Tegison can cause rashes, hair loss, and hepatitis. This drug is also known to cause birth defects and should not be used by women of childbearing age. It has been known to remain in the system for up to three years.