By Alexander E. Bonato, MD — Board-Certified in Internal Medicine · Medically reviewed November 2026.
TL;DR: If your hair is falling out this fall, a seasonal rhythm is a real, documented possibility. In one hair clinic's records of 823 women, the share of resting hairs peaked in July and bottomed out around February, which fits the extra shedding many people notice in autumn. That study can't tell you how much extra to expect, though, and a fall flare can sit on top of pattern hair loss or another trigger. If it's heavy, lasts more than a few months, or comes with thinning, it's worth a proper look.
Every so often a patient will look at my hairline, then at the diplomas on the wall, then back at my hairline. Then they ask, very politely, whether there's a loyalty program on the treatment I obviously haven't started.
Fair question. I'm balding, and I noticed about the time my hairline had already filed for departure. I'm telling you that as a fact, not a pitch.
Anyway. The question I get most in the fall isn't about my hairline. It's this one: why is my hair suddenly falling out?
What's Happening on Your Head, Month by Month
Every hair on your scalp runs on its own schedule. At any moment, about nine in ten are growing and about one in ten are resting. A resting hair hangs around for three to five months and then falls out.2 Normally those schedules are out of sync, so a few hairs fall every day and nobody notices.
Shedding gets noticeable when more hairs than usual end up in the resting phase at the same time, because they let go at the same time too.1,2 Think of it as a flash mob that nobody invited. The question is what gets them to coordinate.
What One Study Found About the Seasons
The best data I could find comes from a hair clinic in Zurich. Over six years, the team went through the records of 823 women who had come in about hair loss and who had no disease or medication that would explain it. Each woman had a trichogram, which means a small sample of hairs is plucked and examined under a microscope to see which phase each one is in.1
The share of resting hairs followed the calendar. It peaked in July, there was a smaller bump in April, and it was lowest around the beginning of February.1 The pattern was statistically solid, and it didn't depend on the woman's age or on which year of the study it was.
Here's how that connects to the fall. A resting hair lasts around 100 days, according to the authors, so a July peak points toward shedding by autumn.1 That step is their reasoning and not something they measured. They counted resting hairs. They didn't count the ones in your hairbrush.
Two things to hold on to. First, these were women who walked into a hair clinic worried about their hair, and about eight in ten of them had female-pattern hair loss. So this isn't proof that every woman sheds in the fall. Second, the paper doesn't say how much extra shedding the seasons add. It shows a rhythm, not a size.
What I find most useful is this. The seasonal swing looked practically identical in the women with pattern hair loss and the women without it.1 That means a fall flare doesn't tell you the cause is only seasonal.
Why the Seasons Might Matter (Nobody Knows Yet)
The authors point to daylight, in the way it changes the hair cycle in other mammals.1 A review of the broader literature mentions a summer-to-autumn rise in shedding and a theory that sunlight is involved, and then says that idea is not scientifically proven.2 Vitamin D has been floated too, as a possible cause. I'd call all of it hypotheses. Anyone telling you the mechanism is settled is ahead of the evidence.
What Else Makes Hair Fall Out
Shedding usually starts two to three months after whatever set it off.2 That delay is why the cause is so easy to miss. The review lists several. Certain medications, usually after about 12 weeks of taking them, including oral contraceptives, beta-blockers, ACE inhibitors, anticonvulsants, antidepressants, and blood thinners. A high fever, surgery, or a serious illness. Childbirth, about three months afterward. Thyroid disease, whether it runs high or low. And a real shortfall in protein, essential fats, or zinc, or crash dieting. For a shortfall in essential fats, the review puts the delay at two to four months.2
A few of the usual suspects are shakier than people assume. The link between emotional stress and shedding is described as unclear, partly because losing your hair is stressful all by itself. Iron is called "very controversial," and vitamin D is only "a possible cause."2 If a measurable deficiency turns up, it should be corrected. Beyond that, I'm not going to tell you a supplement fixes it.
If you take any of those medications, don't stop on your own. Talk to whoever prescribes it. A change like that is a decision to make with a doctor.
The good news is that shedding under six months, called acute, usually settles once the trigger is found and removed.2 Shedding past six months is called chronic, and it mostly affects middle-aged women.2 If you're past that mark, that's the reason to come in and not wait for spring.
Is It Seasonal, or Something Else?
This is where a timeline earns its keep. When did it start? What happened two to three months before: a new medication, an illness, a surgery, a baby, a diet? Is it coming out all over, or is your part widening and the hairs near the front getting finer?
The differences matter. Shedding from a trigger tends to be diffuse, with hairs of normal thickness.2 Pattern hair loss shrinks hairs over time, so the ones that fall and the ones that stay behind get finer. In the office test the review describes, a lot of fine, short hairs in the count points toward pattern loss.2
Here's what that looks like in my office. We talk through the timeline first: life stressors, nutrition, sleep habits, what's changed. Then I look at your scalp. I also do a digital scalp analysis with trichoscopy, using Canfield imaging equipment and HairMetrix software. In plain terms, it's a camera that magnifies your follicles onto a screen. It counts them and measures how thick each hair is, so we're working from numbers instead of an opinion. Then we go over the options.
What Helps, and What Nobody Has Tested
For temporary shedding, the main treatment is finding the trigger and removing it.2 That's less exciting than a serum, and it's the part with the support behind it.
Minoxidil and finasteride are medications for pattern hair loss. The review says neither is effective for this kind of shedding, because neither stops hairs from entering the resting phase or pushes them out of it.2 I didn't find a study in what I reviewed for this post that tested any treatment for seasonal shedding specifically, so I won't pretend there is one.
One more thing from the Zurich authors, because it changes how you read your own results. Seasonal swings can fool a hair treatment. If you start something in a heavy shedding phase, it can look like nothing is working. If you start it in a recovery phase, it can look like it's working beautifully.1 That's a good reason to have someone track it with numbers instead of memory.
Pattern hair loss is a different conversation. We've gone through the evidence for PRP for hair loss and ranked the options in our hair loss treatment comparison, if you want to read ahead.
Frequently Asked Questions
Is it normal to shed more in the fall?
There's real evidence of a seasonal rhythm in the resting phase.1 "Normal" depends on how much, and that's not something a study can tell you about your own head. I wouldn't call a clump in the shower drain normal just because the leaves are also falling.
How long does fall shedding last?
In that study, the resting rate bottomed out around early February, so the cycle swings back through winter.1 The paper doesn't give a number of weeks, and I'd rather not invent one. If it has gone on more than six months, that's called chronic shedding,2 and it's worth looking at.
How do I know if it's seasonal or pattern hair loss?
Honestly, you can't tell from the shower drain. The seasonal swing looked the same in women with pattern loss as in women without it,1 so a fall flare doesn't settle it. A timeline, a look at the scalp, and measurements of the follicles are what separate them.
Should I take biotin or vitamin D?
I didn't find evidence in what I reviewed for this post that either one stops shedding. Biotin deficiency is described as very rare, and the vitamin D link as possible.2 A measurable deficiency gets corrected. A shelf full of hair vitamins isn't a diagnosis.
Will the shedding stop if I start a treatment?
It depends on the cause, and timing can fool you either way.1 Temporary shedding often settles by itself once the trigger is gone. Pattern hair loss doesn't. Which one you have is the first thing to sort out.
Does stress cause it?
The review calls the relationship "ambiguous," because hair loss itself is stressful.2 It's a real and annoying loop. I'd rather help you look at the other triggers too, since those are easier to check.
Come Look at It With Me
Bring your timeline and your questions, and we'll go through it together. We're in Medford, and patients come from Ashland and Grants Pass too. Book a consultation, or read about hair restoration in Medford first. No loyalty program yet. I'm open to suggestions.
References
Kunz M, Seifert B, Trüeb RM. Seasonality of Hair Shedding in Healthy Women Complaining of Hair Loss. Dermatology. 2009;219(2):105-110. doi:10.1159/000216832 (A retrospective study of 823 women at one hair clinic. They came in about hair loss, and about 79% had female-pattern hair loss. It counted resting hairs, not shedding. It reports no effect size in the text. No funding or conflicts of interest are stated.)
Asghar F, Shamim N, Farooque U, Sheikh H, Aqeel R. Telogen Effluvium: A Review of the Literature. Cureus. 2020;12(5):e8320. doi:10.7759/cureus.8320 (A narrative review, not a systematic one. No funding or conflicts of interest.)
