treatment of skin diseases for psoriasis

Long before steroids, there was coal tar. In fact, coal tar has been used in the treatment of skin diseases for over a century. It is the left over by-product of coal processing and distillation. There are thousands of compounds in coal tar, and only a fraction of these are identified. For this reason, it is unlikely that coal tar would be approved by the FDA if presented for new drug status. In any case, coal tar is grandfathered in -- it has been a medication longer than the FDA has existed. Before corticosteroids were first recognized or synthesized for use in inflammatory skin diseases, coal tar was there to help ease the itch. Some of my older professors originally practiced in the pre-corticosteroid era and were very adept at the use of coal tar compounds for skin therapy. Coal tar preparations appear to exert their anti-psoriasis benefits by interfering with DNA and thus slowing down skin cell growth and turnover. The long-term result is thinning of the psoriatic plaques.

Coal tar is found in dozens of over-the-counter psoriasis and dandruff shampoos, as well as creams, gels and bath additives. Compound pharmacists can mix crude coal tar (a black, thick paste) or coal tar solution (an 20% alcohol-based liquid) with all sorts of bases, including steroid creams and ointments. One effective remedy for hand and foot psoriasis is a compound of a steroid with 5% coal tar solution and 2% salicylic acid which a pharmacist can mix up with a prescription from your doctor.
Coal tar is often used in combination with phototherapy, as it sensitizes the skin to ultraviolet radiation. Care should be taken in avoiding excess sun exposure when using coal tar shampoos and other preparations.