Is your scalp itchy or irritated and stubbornly shedding white flakes? You probably have seborrheic dermatitis — more commonly known as dandruff. And you certainly aren't the only one worried about wearing black: Debra Jaliman, MD says that this is the most common scalp issue she sees.Fayne L. Frey, MD, founder of FryFace.com , says up to 50% of the population “experiences dandruff at some point in their lives — usually individuals from adolescence to about age 50, when the sebaceous glands are most active.”So what causes it? "[Dandruff happens] when dead skin cells don’t exfoliate normally, and they build up on the scalp," says Dr. Jaliman. "The scalp gets irritated, and there is peeling.” It can also occur when the scalp is overly dry or overly oily, says Michael Lin, MD, of Dr. Lin Skincare . Or it can be due to skin conditions such as eczema and psoriasis, or even a yeast-like fungus called malassezia.Dr. Lin also says that hair products containing ingredients that irritate the scalp — such as sulfates and drying detergents — can contribute to the problem: “Sensitivity to ingredients in hair care products or hair dyes, especially paraphenylenediamine, can cause a red, itchy, scaly scalp. Washing too often with shampoos that contain harsh chemicals like sulfates or using too many styling products also may irritate your scalp, causing dandruff.” So be sure to check your favorite hair products to make sure they’re not the cause of your flaky scalp.There are a few ways to treat dandruff, although keep in mind that these are treatments and not permanent cures. As Dr. Barry Resnik , founder of Resnik Skin Institute, cautions, “[seborrheic dermatitis] is a condition, not a disease, so it can’t be cured.” That said, there are ways to keep it under control and prevent it from acting up. All the docs we interviewed agree that the best way is to wash your hair with shampoos that contain anti-dandruff ingredients such as selenium, salicylic acid, zinc pyrithione, coal tar, or ketoconazole.Don’t rush things, Dr. Jaliman warns: “I always instruct people to leave the shampoo on for five minutes, so it can completely penetrate the scalp.” Dr. Jaliman advises shampooing more frequently (such as daily or every other day). Dendy Engelman, MD also recommends massaging your scalp for five minutes daily "to loosen the skin” before shampooing. A diet high in antioxidant-rich vegetables can help reduce flare-ups as well, Dr. Resnik says.If anti-dandruff shampoo and diet adjustments don’t do the trick, you may have to break out the big guns. “If there is still peeling and itching...sometimes, a prescription-strength topical steroid lotion or solution is required at night,” says Dr. Jaliman.Dr. Resnik agrees: “More tenacious cases may need a topical cortisone lotion or even oral medicines to knock it out.” So try the shampoo first, and if the problem persists, see your doctor for a prescription. You’ll be back to wearing all black before you know it.