_{Seborrheic dermatitis}

_{In adults seborrheic dermatitis usually affects the scalp, eyebrows, ear canals, sides of the nose, and behind the ears. It sometimes affects the armpits, chest and in the groin area. Most people with it complain of dandruff, especially on the back and sides of the scalp (bad dandruff bad dandruff is usually seborrheic dermatitis).}

_{Stress, fatigue, weather extremes, oily skin and infrequent shampooing or skin cleaning make it worse. Severe medical illnesses, including AIDS, Parkinson's disease, head injury, and stroke are associated with seborrheic dermatitis. These are thought to make the normal skin care that prevents seborrheic dermatitis harder to keep up with. The vast majority of people with seborrheic dermatitis have no associated conditions.}

_{Seborrheic dermatitis may start in infancy as cradle cap. It affects the scalp as thick, crusty, yellow scales. Children outgrow it by age 3 and older do not normally get seborrheic dermatitis. Cradle cap is not contagious, it is not caused by poor hygiene, it is not an allergy, and it is not dangerous. Cradle cap usually does not itch, but it may. If excessive scratching occurs, it can cause additional inflammation, mild infections or bleeding.}

_{The problem in seborrheic dermatitis is in the oil (sebaceous) glands and hair follicles. People with seborrheic dermatitis produce too much sebum (the natural skin oil). Later, pityrosporum yeast, grows excessively in the sebum, sometime along with bacteria, making the dermatitis more persistent.}

_{Seborrheic dermatitis and psoriasis can be difficult to tell apart. Psoriasis tends to have a whiter scale, and affected areas will bleed fairly easily if they are plucked or picked or scratched. Plaques or patches of psoriasis also tend to be thicker and more persistent. Although both can produce dandruff, psoriasis, is less common and more severe. A few people have both conditions, however, which can make diagnosis difficult.}

_{Basic treatment consists of using shampoos containing zinc pyrithione (Head and shoulders, ZNP bar), selenium sulfide (Selsun blue and prescription strength Selsun) or ketoconazole (Nizoral AD and prescription strength Nizoral). You may need to try several shampoos to find the one that works best for you, and then rotate between several medicated and non-medicated shampoos to maintain effectiveness. It's important to massage the shampoo onto the scalp and other affected areas and leave it in place for a few minutes before rinsing thoroughly. Other shampoo ingredients that are sometime helpful are salicylic acid, coal tar, and sulfur.}

_{If shampoos aren't working, the next step is to rub on a prescription cortisone lotion once or twice a day. If you're still having trouble, a coal-tar preparation or overnight medication under a shower cap may be needed.}