Dandruff is a broad term for a flaky, sometimes itchy, scalp. In many cases, it's caused by a buildup of hair care products or dry skin on and around the scalp, something that's easily remedied with a change in shampoo and conditioner. In other cases, the flakes are what's technically known as seborrheic dermatitis.

Seborrheic dermatitis is a type of flaking and scaling of the scalp that's caused, ironically, by excessive oil. (The word seborrhea means “too much oil.”) Seborrheic dermatitis can also create scaly patches on other areas, such as the inside of the ear, face, or torso. A case that develops in an infant is referred to as cradle cap (see Chapter 6).

Seborrhea symptoms can also be associated with yeast overgrowth, although most experts say the condition itself isn't caused by fungus.

Conventional dandruff treatments focus on removing flakes and fighting inflammation; some are also antifungals. Most of the time, doctors recommend OTC remedies, but severe cases might be treated with prescription-strength shampoos or topical cortisone treatments.

OTC dandruff treatments include shampoos made with salicylic acid (see “Acne and Oily Skin,” below), coal tar (a thick, black byproduct of the manufacture of gas and coal that contains known carcinogens), pyrithione zinc, and selenium sulfide; you'll also see antifungal shampoos made with ketoconazole in the dandruff aisle. All can reduce symptoms, but they can cause side effects like stinging or burning and hair loss. Some people also use OTC lotions made with these ingredients, or OTC or prescription steroid creams or lotions, which can cause skin reactions and impair immune function. Here are a few antidandruff herbs: