1. Sudden Hair Loss The trigger is emotional or physical trauma. The shock can cause telogen effluvium, a condition that makes hair stop growing and fall out. "Imagine going bald overnight," says Jessie Cheung, M.D., an assistant professor of dermatology at New York University school of medicine. As your mind and body recover, so too will your hairline. 2. Steady Hair Loss Hair follicles demand a steady infusion of nutrients to sustain rapid growth. If you're shedding more than usual for 2 or 3 months straight, look at your diet: Too little iron, biotin, or zinc can send hair into starvation mode. To restore those nutrients, eat more broccoli, spinach, and eggs. Also, pop a daily multivitamin, such as Centrum. 3. A Round, Smooth Patch A silver-dollar-size bare spot signals alopecia areata. The catalyst is still unknown, but stress and genetics are likely culprits, says Kevin McElwee, Ph.D., an assistant professor of dermatology at the University of British Columbia. See a dermatologist for corticosteroid injections to ease the inflammation causing your hair to hibernate. 4. A Round, Scaly Patch You probably have tinea capitis, a fungal infection. (Think athlete's foot of the head.) Your body battles back with a wave of white blood cells that harm hair follicles. Try an over-the-counter antifungal shampoo, such as Nizoral. If that doesn't work, ask for a prescription antifungal medication, such as Lamisil. Source