Why Does Hair Shed More in the Fall? (The Science Behind Seasonal Shedding)

If you have noticed more hair in your brush, your shower drain, or your pillow once September hits, you are not imagining it. Why does hair shed more in the fall? The short answer is a documented pattern that tends to peak in late summer through early fall before tapering off by winter.

This is not the same as hair loss from a medical condition or the kind of breakage caused by heat and sun exposure. It is a shift in the hair growth cycle itself, and there is a specific mechanism behind it.

The Hair Growth Cycle, Briefly

Every strand of hair on your scalp moves through three phases on its own timeline:

• Anagen, the active growth phase, which can last several years per strand
• Catagen, a short transitional phase where the follicle shrinks
• Telogen, the resting phase, where the strand stops growing and eventually releases

At any given time, roughly 85 to 90 percent of your hair is in anagen and 10 to 15 percent is in telogen. Shedding happens when a telogen hair finally releases from the follicle, a process researchers call teloptosis. Under normal conditions, this happens gradually and evenly across the scalp, which is why healthy hair loss of 50 to 100 strands a day usually goes unnoticed.

Fall shedding happens when more hair than usual sits in that resting phase at once, then releases in a shorter window.

What the Research Actually Shows

Seasonal hair shedding has been tracked in several long term studies, summarized by Donovan Hair Clinic. A 1996 study following 10 subjects over 8 to 14 years found that late summer and early autumn, specifically August, September, and October, showed the highest percentage of hair in the telogen phase, while December through February showed the lowest. A separate study of nearly 2,900 subjects across two years found an increased proportion of telogen hair between July and October, with the lowest rate in January. A later study out of Switzerland tracking over 800 women found the same seasonal curve, with telogen rates lowest in early February and highest in July.

The pattern holds regardless of whether someone has an underlying hair thinning condition, which suggests it is a built in cycle rather than a symptom of something going wrong.

Why Does the Cycle Shift in Fall

The leading explanation involves photoperiod, meaning the amount of daylight hair follicles are exposed to over the course of the year. Researchers believe this signal is processed through the optic pathway and the neuroendocrine system, similar to the mechanism behind seasonal coat shedding in many mammals. As daylight hours shrink heading into fall, more follicles are believed to enter a delayed telogen state during summer, then release together once the season turns.

A second contributing factor is vitamin D. Levels typically peak in late summer from sun exposure, then begin dropping through fall as daylight decreases. Vitamin D plays a role in the hair follicle cycle, and low levels have been associated with telogen effluvium in some research, so the fall shed may partly reflect stores starting to decline.

A third factor is simply the cumulative toll of summer itself. UV exposure, heat, and increased styling during summer months put additional stress on the scalp and hair shaft, which can compound the natural seasonal shift rather than cause it outright.

How to Tell Normal Seasonal Shedding from Something Else

Typical seasonal shedding has a recognizable pattern:

• It is diffuse, meaning it is spread evenly across the scalp rather than concentrated in one spot
• It clusters around late summer into fall, generally peaking around September
• It resolves within a few weeks to a couple of months rather than continuing indefinitely
• Overall density and your part look about the same once it settles
• It tends to repeat the same way each year if you look back

If shedding is patchy, concentrated at the hairline, lasts well beyond a couple of months, or comes with scalp irritation, that points toward a different cause and is worth discussing with a doctor or dermatologist rather than waiting it out.

Supporting Hair Through the Seasonal Shed

You cannot override the hair cycle, but you can support the follicle environment and reduce factors that make shedding worse than it needs to be.

Support the scalp directly. A healthy follicle needs steady circulation and a clean, balanced scalp environment to move efficiently from telogen back into anagen. Ingredients like biotin and niacinamide support the keratin production process during that transition.

Address summer's leftover damage. Hair that is already weakened from UV exposure and chlorine earlier in the season is more likely to break during a heavier shed, which can make normal shedding look more dramatic than it is. Rebuilding protein with ingredients like hydrolyzed collagen helps strands hold on through the transition.

Keep an eye on nutrient intake. Since vitamin D and overall nutritional status are tied to the hair cycle, a diet with adequate iron, protein, and vitamin D, or a supplement if levels run low, supports the follicle heading into the shorter days of fall and winter.

Be gentle during peak shed weeks. Reducing tension from tight hairstyles and minimizing unnecessary heat styling during the heaviest shedding weeks reduces the amount of hair lost to mechanical stress on top of the natural cycle.

When the Shed Should Resolve

Based on the research pattern, fall shedding typically runs from around August through October, with the heaviest weeks generally falling in September, before tapering back down toward the low point in December through February. If shedding is still elevated well past that window, it is reasonable to look at other causes, including stress, thyroid function, or nutrient deficiencies, rather than attributing it to the season indefinitely.

How Kerotin Supports Hair Through Seasonal Transitions

Kerotin's Hair Growth Vitamins and Hair Growth Spot Serum are formulated to support the follicle environment through phases where shedding naturally increases, pairing biotin and scalp supporting ingredients with consistent use through the season rather than a one time fix. Since the fall shed is cyclical, the most effective approach is a routine that carries through the transition, not a reaction once shedding has already picked up.

Frequently Asked Questions

Is it normal for hair to shed more in the fall? Yes. Multiple long term studies have found that the percentage of hair in the resting phase peaks in late summer through early fall, with shedding tapering off by winter. This pattern shows up regardless of whether someone has an underlying hair thinning condition.

How long does seasonal hair shedding last? For most people, seasonal shedding runs a few weeks to a couple of months, generally peaking around September, before returning to a normal baseline.

What causes hair to shed more as days get shorter? Researchers point to photoperiod, the change in daylight hours, as a likely trigger processed through the neuroendocrine system, along with declining vitamin D levels as sunlight exposure drops through fall.

Should I be worried about fall hair shedding? Typical seasonal shedding is diffuse, temporary, and resolves within a couple of months. Shedding that is patchy, concentrated in one area, or lasts significantly longer is worth discussing with a doctor rather than assuming it is seasonal.

Can supplements help with seasonal shedding? Supporting the follicle with biotin, adequate protein, iron, and vitamin D can help hair move through the cycle more efficiently, though supplements do not stop the natural seasonal pattern itself.

References

1. 1. Courtois, M. et al. (1996), cited in "Celebrating the End of Another Cycle of Seasonal Shedding." Donovan Hair Clinic. https://donovanmedical.com/hair-blog/October