Every autumn, a slightly higher percentage of your hair enters the same phase at once, and you notice it in the shower, on the brush, on the pillow. There's a real mechanism behind this, and it has a name in at least one language, which is more than English can say for it.
The mechanism, plainly
Hair grows in three distinct phases. Anagen is active growth, lasting anywhere from two to seven years depending on the hair and the person. Catagen is a short transitional phase, two to three weeks, where growth stops. Telogen is the resting phase that precedes shedding, lasting around three months before the hair actually falls and a new one begins the cycle again underneath it.
At any given moment, roughly 10 to 20 percent of the hair on your head is sitting in telogen. Losing 50 to 100 hairs a day is entirely normal turnover, not loss in any meaningful sense.
What changes in autumn is the proportion. Summer heat and UV exposure tend to accelerate hair into an extended growth phase — more hair, growing faster, for longer. The trade-off arrives roughly two to three months later: a larger cohort of hairs hits the end of that accelerated cycle simultaneously, and moves into telogen together instead of on the usual staggered schedule. The result is a temporary spike, often reaching or exceeding 100 hairs a day, typically for four to six weeks between September and November. The exact biological triggers are still not fully mapped — researchers point to UV damage, the sharp shift in temperature and humidity, and even the resumption of stress and routine after summer as compounding factors, rather than one single clean cause.
A name for it, elsewhere
Japanese has a term that English doesn't bother with: 換毛期, kan-mō-ki. It's the same word used for animals — a dog or a horse shedding a lighter summer coat to grow in a denser one for winter, and the reverse in spring. Applied to human hair, it's less a diagnosis than a description: this is a coat change, not a malfunction.
The distinction shows up in how the two cultures talk about care, too. Western sources tend to frame this as something to manage or treat — an anti-shedding product, a course of action. Japanese sources lean toward a simpler premise: 頭皮も肌の一部です, "the scalp is part of your skin too," meaning it deserves the same daily attention as your face gets, not a special intervention only once symptoms show up. Scalp massage to stimulate circulation is one of the few pieces of advice that shows up consistently on both sides, in every source, regardless of country.
What we'd actually suggest, if asked
A scalp going through kan-mō-ki isn't the only thing worth attention right now — the hair itself benefits from a fall trim more than people assume. Ends that have spent a summer in salt water, chlorine, and sun are usually the most damaged part of the hair by September, and trimming them off does two things at once: it removes hair that was already compromised before it had a chance to split further, and it gives the new growth coming in through kan-mō-ki somewhere healthier to land, instead of blending into ends that were already struggling.
Fall is, in other words, a genuinely good moment to come in — not because anything is wrong, but because it's the point in the year where a trim does the most work for the least hair lost.
Past that, the same scalp logic applies here as anywhere: circulation and a well-cared-for follicle environment give whatever grows in next a better foundation. Ask about a scalp treatment next time you're in the chair — it's a small addition to a normal appointment, and it's exactly the right season for it.
None of this stops kan-mō-ki. It isn't meant to — the hair currently shedding has already made that decision, weeks ago, without asking anyone. What a good trim and a bit of scalp attention actually do is quieter and slower: give the next cycle a healthier start, both from the root and from the ends. It's meant to meet the season with attention instead of alarm.
Is losing more hair in fall normal?
Yes. It's a well-documented seasonal pattern, not a sign of a problem. A larger share of hair enters its resting phase at once in autumn and sheds together, rather than on the usual staggered schedule.
Why does hair shed more in autumn than other seasons?
Summer heat and UV exposure tend to push hair into an extended growth phase. Two to three months later, that same hair reaches the end of its cycle simultaneously, producing a temporary spike in shedding.
How long does seasonal hair shedding last?
Typically four to six weeks, usually falling somewhere between September and November.
Can scalp care actually reduce fall hair loss?
Not the hair currently shedding — that decision was already made weeks earlier. What scalp care does is give the next growth cycle a better environment to grow in, through improved circulation and a well-maintained follicle.
What does the Japanese term kan-mō-ki mean?
換毛期 (kan-mō-ki) is the term used for animals shedding a summer coat before growing in a winter one. Applied to human hair, it describes the same idea: a seasonal changeover, not a malfunction.
Is fall a good time to get a haircut?
Yes. Ends damaged by a summer of sun, salt water, and chlorine are usually at their weakest by September. Trimming them now removes hair that was already compromised and gives new growth somewhere healthier to land.