The symptoms: Seborrheic dermatitis causes the scalp to shed its skin, so you'll notice greasy, yellowish scales on your shoulders or in your hair. It may be the result of yeast called Malassezia, hormonal changes, or excess oil in the skin. Psoriasis, an autoimmune condition that causes excessive skin cell turnover, produces a very thick white scale on the scalp that can bleed if pulled off. With ringworm, a fungus you contract by touching an infected person or animal, you'll notice red patches on your scalp, which may be diffuse, Jakubowicz says.
The tests: A physical exam of the scalp will help determine which condition you have. A fungal culture and possibly a biopsy of the scalp may pinpoint ringworm.
What you can do: Each condition usually requires a prescription: a medicated shampoo for seborrheic dermatitis, medications or light therapy for psoriasis, and oral antifungals for ringworm.
Alopecia areata is an autoimmune disorder in which the immune system attacks hair follicles. It affects about 4.7 million people in the United States and occurs equally in men and women. The cause is unknown, but it may be triggered by stress or illness.
The symptoms: The condition can occur in three forms. Alopecia areata commonly causes round, smooth patches of baldness on the scalp, eyebrows, or legs, Dr. Fusco says. Total hair loss on the head is known as alopecia totalis, while hair loss that occurs all over the body is called alopecia universalis. "Some patients have reported that before the bald spot occurred, they felt something in that area—a tingling or an irritation," Dr. Fusco says.
The tests: Observing the pattern of hair loss can usually determine if you have alopecia areata, and blood tests for iron stores, ANAs. and hormones are usually done to rule out underlying conditions that may cause hair loss.
What you can do: Alopecia areata is usually treated with intralesional corticosteroids, Dr. Fusco says. In some cases, minoxidil (Rogaine) may also help. It's also important to reduce stress.
*** More from Prevention:
Too much shampooing, styling, and dyeing can harm your tresses. Heat and chemicals weaken the hair, causing it to break and fall out. Often, it's a combination of treatments—keratin, coloring, and blow-drying, for instance—that does the damage.
The symptoms: If the fallout is occurring from external damage caused by styling, it will simply break, and you won't see those club-shaped telogen bulbs at the ends.
The tests: Dr. Jakubowicz does a pull test: She takes a small handful of about 50 strands, pulls gently, and checks to see whether the hair that comes out has bulbs on the ends.