Dandruff is the shedding of dead skin cells from the scalp. The signs and symptoms of dandruff are an itchy scalp and flakiness, and sometimes also red and greasy patches of skin and a tingly feeling on the skin. Dandruff can have several causes, including dry skin, seborrhoeic dermatitis, not cleaning/scrubbing often enough, shampooing too often, psoriasis, eczema, sensitivity to hair care products, or a yeast-like fungus. Dry skin is the most common cause of flaking dandruff. A number of antifungal treatments have been found to be effective including ketoconazole, zinc pyrithione and selenium disulfide. Other effective anti-dandruff agents include salicylic acid, sulfur, and coal tar.