Seasonal Hair Shedding Is Real: What Six Years of Trichograms Show

Seasonal hair shedding is a documented biological pattern, not an old wives' tale. In a six-year study of 823 healthy women published in the journal Dermatology, researchers led by Dr. Michael Kunz at University Hospital of Zurich found annual periodicity in hair growth and shedding, with the proportion of resting, or telogen, hairs highest in summer and lowest in late winter. Translation: many scalps release the most hair in late summer and early autumn.

What Did the Six-Year Study Actually Find?

The study, published in 2009, was a retrospective review of women who complained of hair loss but turned out to be otherwise healthy, with trichograms, microscopic hair counts, taken over six years. The study record at PubMed summarizes the result: analysis of trichograms demonstrated annual periodicity in the growth and shedding of hair, manifested by a maximal proportion of telogen hairs in summer, with a less pronounced second peak in spring and the lowest telogen rates in late winter. The authors concluded the findings confirmed seasonal changes in human hair growth in a representative number of women for the first time.

Hair grows in cycles, and telogen is the resting phase that ends with the hair falling out. Each follicle is on its own clock, so a synchronized rise in telogen hairs across the scalp shows up in the brush and the drain a few weeks later. A seasonal uptick in shedding therefore reflects hairs that entered rest months earlier, not something the weather did to the strand last week.

How Much Shedding Is Normal in Autumn?

Dermatologists commonly cite a baseline of roughly 50 to 100 hairs shed per day, and seasonal peaks push that number visibly higher for a few weeks. Dr. Jeff Donovan, a board-certified dermatologist specializing in hair loss, reviewed the seasonal shedding literature on his clinic's site and reports consistent findings across studies: one study found telogen rates lowest at the beginning of February and highest in July, and another showed the highest proportion of telogen hairs in September and the lowest in January, per his review of seasonal shedding research.

The pattern repeats predictably enough that researchers have detected it in population data, not just clinic visits. Searches for hair loss online peak in summer and early autumn in search-trend analyses of dermatological topics. For the reader, the practical signature of seasonal shedding is a diffuse increase lasting several weeks, in autumn most classically, that resolves on its own and does not produce bald patches or a visibly receding hairline.

How Is Seasonal Shedding Different From Hair Loss That Needs a Doctor?

Pattern and progression separate the benign from the concerning. Seasonal shedding is diffuse and temporary, while conditions such as telogen effluvium from illness, stress, or nutritional deficiency produce a more abrupt and dramatic shed, and androgenetic alopecia thins in a pattern, at the crown and part lines, rather than all over. Sudden widening of a part, visible scalp through the hair, or shedding that continues past three months warrants a dermatologist visit rather than patience.

The table's right column is not a reason for panic; it is the threshold at which measurement beats waiting. Dermatologists can order ferritin, thyroid, and vitamin D levels and examine the scalp directly, which no seasonal heuristic can do.

Does Cold Weather or Sun Damage Hair Separately From Shedding?

Shedding is only one seasonal variable. Cold outdoor air plus indoor heating drops humidity, and dry hair loses flexibility, which raises breakage risk during winter styling. The same Zurich team's findings on a spring peak suggest the scalp's calendar is not perfectly uniform from person to person, so a winter with more breakage but not more shedding is a moisture problem, not a follicle problem.

A seasonally adjusted routine follows the failure mode. In dry months, dermatological guidance for hair mirrors skin care: less frequent harsh cleansing, more conditioning, and physical protection such as satin or silk pillowcases and tucked-in styles against wind and sweater-fabric friction. In humid months, scalp comfort, not strand moisture, becomes the focus, since sweat and oil accumulation drive the itch and flaking that push people toward over-washing. Neither adjustment changes how many hairs fall out; they change how the surviving strands look and feel.

Can You Do Anything About Seasonal Shedding?

The honest answer is that the shedding itself does not need fixing, because the follicles that released those telogen hairs are already growing replacements. What a routine can influence is the condition of the hair that remains and the scalp it grows from. Dr. Donovan's review frames autumn shedding as self-limiting, and the dermatological consensus is that reassurance, not treatment, is the standard of care for the pattern documented in the Zurich trichograms.

Gentle handling during peak shedding weeks is the one intervention with a mechanical rationale. Hair that is about to shed releases with less force than a healthy anagen hair, so aggressive tight styles, rough brushing on wet hair, and high-tension drying accelerate loss that was coming anyway while stressing the strands staying behind. Washing less aggressively, detangling saturated hair with a wide-tooth comb, and loosening styles during August-to-October cost nothing and lower background breakage.

Supplements marketed for seasonal shedding deserve skepticism. No vitamin overrides the follicle's calendar, and excess iron or biotin supplementation without a documented deficiency carries its own risks, including lab interference, a point dermatologists raise about high-dose biotin. Where a deficiency exists, correcting it matters for hair; where none exists, the evidence does not show a benefit, and a blood test through a physician is the only way to tell the two situations apart.

What Should a Reader Take Away?

Autumn brush-clearing, within limits, is biology doing what six years of trichograms showed it does. The evidence-supported response is to not panic, not to buy a supplement shelf, and to watch the pattern across weeks. Diffuse shedding that arrives with the season and leaves with it fits the documented rhythm; shedding that breaks the rhythm deserves a professional look, ideally before the next seasonal cycle muddies the picture.