Retinoids normalize DNA activity in skin cells, thus decreasing the cell proliferation of psoriasis and normalizing abnormal cellular growth in the hair follicle that is a contributing cause of acne. Local skin irritation is the most common side effect, which may be reduced by use of a topical steroid. Although the possibility of birth defects is much lower for topical retinoids than for the systemic forms, women who are pregnant or who may become pregnant should use topical retinoids only under close medical supervision. Vitamin D Analogues . The analogue calcitriol may also be given systemically.
Local irritation is the major side effect of topical vitamin D analogues.
Since vitamin D can affect growing bone, vitamin D analogues should be used with special care in children. Steroids also have immunosuppressive and antiproliferative effects that add to their effectiveness in psoriasis. Even topical steroids may have systemic effects if used over long periods of time. Topical steroids are usually prescribed for selected purposes for limited periods of time, and are frequently used in combination with other agents. Regular skin care with moisturizing and lubricating agents prevents skin dryness during and between periods of psoriasis therapy.