We like to think of our hair as permanently attached to our head, but that’s not exactly how it works. Each hair goes through its own cycle of growing, waiting around, and then falling out. So that explains why you’ll find hairs in your hairbrush. But how do you know how much is too much?
The normal amount of hair to lose
According to the American Academy of Dermatology, a typical loss is 50 to 100 strands per day. We’ll understand if you don’t count them all individually.
Note that this is an average. If your hair is coarse, curly, or tangles easily, your lost hairs may just be hanging out on your head, clinging to their friends in those curls or tangles. When you take the time to do a thorough washing or combing, you may find that a lot of hair gets released all at once. That’s not because it all fell out on wash day, just that you’re seeing several days’ worth of shedding at once.
When it might be more, and still normal
Aside from your hair care schedule, there are other reasons a larger-than-usual loss of hair might be perfectly normal.
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One is pregnancy. It’s common to lose less hair than usual while you’re pregnant, and for the hair to begin to fall out about two months after the pregnancy ends. (Hair loss peaks at about four months post-pregnancy.) You’re not losing all your hair, it’s just returning to normal growth patterns thanks to hormonal fluctuations. A similar situation can happen when you stop taking birth control pills.
You can also shed more hair than usual due to stress. This could include weight loss (more than 20 pounds), illness especially if it involved a fever, or recovery from an operation, according to the AAD.
When it might be more, and signal a problem
Everything we’ve talked about above is considered hair shedding. But you’re probably here because you’re worried about hair loss.
The difference is that in hair shedding, each hair you lose is quickly replaced by another. Pregnancy and stress can affect the rate at which individual hairs mature and grow, but you’ll still grow more hair after those are lost.
But there are also medications that can cause hair loss, either permanently or temporarily. For example, chemotherapy for cancer treatment can interfere with hair growth; typically the hair starts growing back after treatment has finished.
Other medications that can increase your chances of hair loss include retinoids and antidepressants. If you’re losing more hair than you would expect, and you think it may be related to medication, discuss the situation with your doctor. There are also medical conditions that can cause hair loss, like the autoimmune disease alopecia areata.
Hair loss can also be genetic, as in “male pattern baldness,” which requires the genes for it but is also accelerated by high levels of testosterone. (Women can get this too, but less commonly.)
Hairstyles that pull on the hair can damage the hair, causing it to break or fall out, and over the long term can damage hair follicles enough that the hair stops growing back. If you pull your hair out due to stress or for other reasons (like tweezing your hairline) that can also cause hair to fall out and not necessarily grow back.