Dandruff is the shedding of excessive amounts of dead skin from the scalp. Dandruff usually leads to some degree of scalp itching, but sometimes there is no redness or other skin abnormalities. The cause of dandruff is unknown, but may be related to the overgrowth of certain yeasts on the scalp. The yeasts grow on the skin of nearly everyone, but some people are susceptible to an overgrowth that can lead to itching and dry, flaky skin.
Dandruff often shows up as white flakes on dark clothing. Severe dandruff may be due to seborrheic dermatitis. This may be suspected if the scalp is red, or there is greasy scaling on the scalp, behind the ears, or on the face (eyebrows, sides of the nose).
There is no known prevention for the condition. Dandruff usually worsens in dry, winter weather and improves in warm, humid conditions. Dandruff may also worsen during times of stress.
Dandruff cannot be cured, but it can be controlled with regular hair washing, particularly with medicated shampoos. Effective dandruff shampoos might include the following ingredients: selenium sulfide (Selsun Blue), zinc pyrithione (Head & Shoulders, ZNP), ketoconazole (Nizoral AD), tar (T/Gel, Pentrax) or sulfur (Sebulex). Seborrheic dermatitis is a related condition that can be controlled with prescription medications, including prescription-strength shampoos.