What is the best way to treat severe dandruff?

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Q. I have had a dandruff problem for years. I have tried selenium and zinc shampoos, as well as ketoconazole shampoo. Nothing has worked. Are there other options?

A. Dandruff, which is a chronic skin condition known as seborrheic dermatitis of the scalp, can range from a minor irritant to a severe rash of the entire scalp.

It is caused when a skin fungus called Malassezia irritates the sebaceous glands of the scalp. This triggers an immune response, which leads to a scaly rash. The first step for treatment is similar to what you have tried: over-the-counter dandruff shampoos, containing zinc, selenium, or ketoconazole. For maximum benefit, the shampoos should be left on the scalp for five minutes before rinsing. Coal tar shampoo is also effective, although it may discolor light-colored hair.

If all these treatments do not work, you need prescription-strength medication. A topical corticosteroid, such as fluocinolone (Capex), may be used for two-weeks to quiet the rash. Another effective class of medications is calcineurin inhibitors like tacrolimus (Protopic) and pimecrolimus (Elidel), which help to suppress the immune response. It's essential to apply these medications properly, so talk with your doctor about these options.

— by William Kormos, M.D.
Editor in Chief, Harvard Men's Health Watch