The Scientist: Amy McMichael, M.D., Chair of the department of dermatology at Wake Forest Baptist Health in Winston-Salem, N.C.
If you have super-straight hair, a lot of the hairs you shed will end up on your clothes, in your hairbrush or on the floor. The rest will come out when you suds up. If you have curlier hair, shed strands often get caught in their stable neighbors and might not be freed until you wash your hair—probably a few times a week at most—and that means you could conceivably pull out significantly more than a hundred hairs in a single shower. And if that hair is long and thick, the mass of strands in the drain is going to look especially scary.
If you’re worried that you might be suffering clinical hair loss as opposed to regular shedding, the true indication will not be the amount of hair that comes out, but whether that amount has changed. If you’re noticing more hair than normal in the drain, if it’s coming out in clumps, if your ponytail feels thinner than it used to, or if you can see more of your scalp than you could before, you should consult a dermatologist.