Oh my! Many parents bring in their babies with a thick, scaly crust on their head. This is usually cradle cap. The fancy (medical) name for this is seborrheic dermatitis. The scaling, redness, and itching occurs most often on the scalp and face (often in the eyebrows). On infants, cradle cap often resolves spontaneously, without treatment. Cradle cap peaks at 2 and at 12 months of age. It also may occur in adolescence and early adulthood.
Treatment of infantile seborrheic dermatitis is primarily rubbing emollients that help loosen scales. Good examples of emollients are mineral oil, olive oil or petroleum jelly. The scales can then be removed by rubbing with a cloth or an infant hair brush. Ketoconazole is an antifungal cream that can also be used and is thought to be safe. The FDA has not approved any medicated shampoos for children younger than two years.
If you get this as an adolescent or an adult, over-the-counter shampoos and topical antifungals (like ketoconazole) are helpful. It is more common in men and is typically more severe in cold and dry climates and during periods of increased stress. Seborrheic dermatitis is a chronic condition and so ongoing maintenance therapy is often necessary.
There are lots of other skin conditions that can be flaky on the scalp so if the above treatment does not work, see your doctor.