context: If your scalp itches and flakes, your doctor can tell if it's just dandruff or a more serious problem like psoriasis, a disease that causes red, scaly patches on your skin. Once you have the right diagnosis, you can treat the cause and get some relief. Dandruff is a common skin problem. You may notice flakes that fall off your scalp and cling to your hair or land on your clothing. Your scalp may itch, too. Several things can cause dandruff: Seborrheic dermatitis: This is oily, itchy, irritated skin that flakes off on your scalp. It also can happen with your eyebrows, groin, or chest hair. Contact dermatitis: Hair care products like shampoo, gel, or dye can irritate your scalp and cause redness, itchiness, and flakes. Fungus called malassezia is a yeast that thrives on the oil on your scalp. If you don't shampoo your hair often enough, oily skin can flake off. Dry skin can lead to small flakes on your scalp. You'll probably have dry skin all over your body. Male hormones: Men are more likely to get dandruff than women. People whose immune systems can't fight off diseases, for instance people who have HIV, may be more likely to get dandruff. Dandruff usually isn't serious. You can't catch it from anyone else or pass it on. It can be uncomfortable or embarrassing, though. Psoriasis can affect your scalp, and the red, scaly patches it causes can flake off like dandruff does. There are a few differences, though: It's chronic: Psoriasis is long-lasting while dandruff may come and go. It's more scaly than flaky. If it's mild, scalp psoriasis looks like scaly, silvery, or powdery patches that may come off in tiny pieces. More serious outbreaks can be red and painful. It may spread. Psoriasis patches can creep past your hairline to your forehead, the back of your neck, or the skin around your ears. You may have psoriasis patches on other parts of your body, too, like your elbows, legs, feet, palms, or back. It's an autoimmune disease. Psoriasis is caused by your body's immune system: White blood cells that should fight off diseases attack your skin cells instead. Your doctor may figure out the reason your scalp flakes or itches just from your symptoms. To be sure, she may look at a small piece of skin from your scalp under a microscope or send it to a lab. If you have mild dandruff because your scalp is greasy or oily, you may just try a regular, gentle shampoo. If that doesn't help, some shampoos are made to control dandruff. They may have zinc pyrithione ( Head & Shoulders, Free & Clear), coal tar ( Neutrogena T/ Gel), salicylic acid ( Neutrogena T/ Sal), selenium sulfide ( Selsun Blue), or ketoconazole ( Nizoral). Tea tree oil is an alternative treatment for dandruff. Follow the directions on the shampoo bottle. Your doctor or pharmacist can point you to the right shampoo for you. You also can get a prescription dandruff product if over-the-counter shampoos don't stop your itch and flakes. Coal tar and salicylic acid shampoos or scalp treatments may also help with mild scalp psoriasis. Topical creams, ointments, and foams like the following can slow psoriasis skin buildup and ease red, scaly patches on your scalp. They may have vitamins or steroids to calm the inflammation: Anthralin ( Zithranol- RR) Calcipotriene ( Dovonex) Calcipotriene and betamethasone dipropionate ( Taclonex) Calcitriol ( Vectical) Tazarotene ( Tazorac) Your doctor can also put steroids (strong anti-inflammatory drugs) into the patches on your scalp if your psoriasis is milder or just in a few spots. If you have severe psoriasis, you may need stronger drugs. These include methotrexate, which affects how certain cells grow; cyclosporine, which slows down your immune system; biologics, which target specific areas of your immune system; or oral retinoids, which are high doses of vitamin A. You can also try ultraviolet or UV light treatments to control your psoriasis patches. You can part your hair in rows so UV light from a special lamp can reach your scalp or use a handheld UV comb that beams the light directly to your scalp.