Dandruff may be the result of a dry scalp, or a skin condition called seborrheic dermatitis. It could also be caused by eczema, psoriasis, or, very commonly, an overgrowth of a yeastlike fungus called malassezia. (Here are surprising reasons you may be suddenly prone to dandruff
). Drugstore remedies might include shampoos with zinc pyrithione, which targets fungus and bacteria; ketoconazole, which also fights fungus; coal tar and selenium sulfide, which slow the growth and die-off of skin cells on your scalp; and salicylic acid, which loosens flakes so they can be washed away. For natural treatments, read on.