Dandruff: A scalp condition that produces white flakes that may be shed and fall from the hair. One cause of dandruff is overworking of the sebaceous glands. Another cause of dandruff is fungus, especially an abundance of the fungus Pitrosporum ovale. If several weeks of using a good-quality shampoo does not stop the dandruff, treatment options include an antifungal shampoo such as Denorex, DHS Targel, ionil-T plus, MG217, Neutrogena T/Gel, Scalpicin, Sebulex, Selsun Blue, Tegrin, or Zircon. The active ingredients approved for dandruff treatment by the US Food and Drug Administration (FDA) include tar, pyrithione zinc, salicylic acid, selenium sulfide, sulfur, and ketoconazole.