Dandruff is a skin condition that mainly affects the scalp. Symptoms include flaking and sometimes mild itchiness. It can result in social or self-esteem problems. A more severe form of the condition, which includes inflammation of the skin, is known as seborrhoeic dermatitis. The cause is unclear, but believed to involve a number of genetic and environmental factors. The condition may worsen in the winter. It is not due to poor hygiene. The underlying mechanism involves the excessive growth of skin cells. Diagnosis is based on symptoms.