The most common cause of dandruff is the fungus Malassezia furfur (previously known as Pityrosporum ovale). This fungus is found naturally on the skin surface of both healthy people and those with dandruff. The fungus feeds off of sebum, and is consequently found most on skin areas with many sebaceous glands: on the scalp, face and upper part of the body. When Malassezia furfur grows too rapidly, the natural renewal of cells is disturbed and dandruff appears with itching. Mild dandruff may be caused by overactive sebaceous glands which are triggered by hormonal imbalance or stress.

Other causative factors include family history, food allergies, excessive perspiration, use of alkaline soaps and yeast infections. Even the season of the year can contribute to the problem: Cold, dry winters are notorious for bringing on dandruff or making it worse. Symptoms of dandruff can also be aggravated by exposure to dust, UV light, harsh shampoos, and hair dyes.