September Shedding: Why Your Hair Falls Out More in Autumn
If you live north of the equator, shedding season is here. Seasonal shedding can kick in anytime from late August right through October, and it's one of the most common things I get asked about at this time of year.
More hair in the plughole, more on your brush, more on your jumper. It's unsettling. So let's talk about what's actually going on, what the research does and doesn't tell us, and when it's worth getting checked rather than waiting it out.
First: not all autumn shedding is seasonal
Before we get into the science, this is the bit I most want you to hear. Not everyone shedding more right now has seasonal shedding.
Hair can shed for lots of reasons, including:
Stress
Low iron
Thyroid disease
Medications
Weight loss
Illness
Other hair loss conditions
So more hair in your brush this month isn't an automatic explanation. It's a prompt to look a little closer.
What actually causes seasonal shedding?
The leading theory points to daylight. Longer, brighter days over summer seem to prolong the resting (telogen) phase in a portion of your follicles. This is known as delayed telogen release.
In other words, those hairs held on through the summer. As daylight hours shorten into autumn, they finally let go, and more strands shed around the same time.
It’s a normal, cyclical pattern, not a sign that anything has gone wrong.
Is it vitamin D? Probably not
The moment people hear "daylight" or "sun", I get asked about vitamin D. Honestly, there's no good evidence yet that vitamin D plays a big role in seasonal shedding.
What may matter more are hormones such as prolactin, along with other hormones from the hypothalamus and pituitary gland. The truth is, the science hasn't fully figured this one out yet, and I'd rather tell you that than pretend otherwise.
Seasonal shedding vs triggered shedding
These two get mixed up constantly, but they're different things.
Seasonal shedding is driven by changing daylight. It doesn't need a personal trigger.
Triggered shedding (telogen effluvium) is caused by something that happened to you, such as illness, a high fever, major stress, crash dieting, rapid weight loss, GLP-1 medication or childbirth. It also has a delay: the trigger pushes follicles into rest, but the hairs don't fall until that resting phase ends, usually 6 to 12 weeks later.
So if you're shedding heavily in September and suspect a trigger, think back to June or July, not this week.
Is it shedding or breakage?
It's worth checking, because the fix is completely different.
Shedding: the hair comes out from the scalp with a small white bulb at the root. That's a hair that has completed its growth cycle.
Breakage: the hair snaps somewhere along the length, with no bulb. That's damage from heat, chemical processing, dryness or rough handling.
Breakage needs a haircare fix. Shedding needs a look at your health and possible triggers.
How long does it last?
For people with true seasonal shedding, things usually settle back to normal by December or January. If it's seasonal, it's temporary.
As a guide, losing 50 to 100 hairs a day is normal turnover across roughly 100,000 follicles.
The pattern matters more than the number.
When to get it checked
Online content is great for reassurance, but it can't assess your scalp. Book a proper assessment if you notice any of these:
Shedding that lasts more than 3 months
Visible thinning at the parting or temples, or more scalp showing through
Patchy loss rather than an all-over shed
Clumps coming out with a gentle tug
Itching, flaking or soreness alongside the shedding
A trichology assessment can include a pull test, density checks and sometimes blood tests, so you get an actual answer rather than a guess.
