But Dr. Fusco points to other negative (and preventable) factors that have an impact on women's scalp health. "A trend I have issue with is women who are dramatically decreasing their shampooing and instead are substituting dry shampoo," she says. "[A] healthy scalp and beautiful hair are linked, and nothing cleans hair and scalp like a wet shampoo." Shampooing exfoliates your scalp, which keeps your hair follicles in tip-top shape. "I often get asked how often one should shampoo and the answer is different for everyone," Dr. Fusco says. "But I recommend at least once a week for most and twice a week for those with dandruff."The act of shampooing is what causes most of your hair to fall out, but it also sheds during combing, brushing, touching, and friction. "You should lose 100 to 150 hairs a day," Dr. Fusco explains. Visually, that looks like about the size of a golf ball when you roll it all up together (ew), but it varies depending on hair type and length.If that's what you're seeing, you're cool as a cucumber. But if you have a visible bald spot, the shedding is more than 100 hairs a day for more than a month, or your hairdresser comments on your hair loss, it's time to figure out the problem. Dr. Fusco once again stresses the importance of consistent, proper scalp and hair care. "Zinc pyrithione is an ingredient to look for," she says. It is an anti-dandruff ingredient used in a whole host of "hair-healthy" shampoos, like Head & Shoulders. Since it prevents dandruff, it keeps the scalp healthy, which leads to better hair growth and retention. If you're looking for a product that doesn't smell like something your derm would give you, Dr. Fusco suggests Clear's Complete Care Line — that's the brand she consults on.Vitamin deficiency may also play into hair loss. Women with iron deficiencies or diets that are low in protein should supplement if their doctor gives the okay. Also, make note of any changes in your hormone levels. " Spironolactone will benefit individuals who are experiencing certain hormonally connected hair losses," she says. But again, check in with your doc before you start popping any type of pill or supplement.Typically, hair loss is a completely normal process and, with the right mix of shampooing and healthy diet, can be controlled. Just make sure to clean up whatever does fall out of your head from the drain. That's just good roommate karma.