If you find hairs in the bathtub after a shower or you find hairs stuck in your comb, don't worry; you're not necessarily going bald. And yet if you kept track of all the hairs you found over a period of a few years, it would seem that what's left on top must be getting thinner. In fact, hairs fall out naturally all the time. And, like leaves or pine needles, each hair goes through a cycle of gradually growing out and eventually falling off.
A new hair begins near the surface of the skin and starts out like the "peach fuzz" on the upper lip of an adolescent boy. As the hair grows out, it thickens and the follicle grows deeper. In its final stage, the hair coming out of the follicle gets thinner and becomes less firmly attached. At this point, the hair falls out easily.
Generally we lose between twenty-five and a hundred and twenty-five hairs per day. Most of the time, new hairs grow from the old follicles. For some reason that's not entirely understood, men tend to go bald on the tops and fronts of their heads. Actually, the hair doesn't go away completely; it just becomes arrested in the early, peach-fuzz stage. As full-length hairs fall out naturally, the follicle produces only a tiny replacement that will never grow to full size.
Women don't tend to go bald, but as they get older, their hair gets thinner by the same process. Of course, if you're losing a lot of hair in a short time, you may have a scalp problem and should probably see a doctor, but a few hairs in the bathtub shouldn't raise any alarms.