Is Seasonal Hair Shedding Actually a Thing? What the Science Says

Hair shedding is a normal part of the hair-growth cycle.

But when you suddenly notice more hair in your brush, shower or on your pillow, it can be difficult to know whether you're experiencing ordinary shedding, seasonal hair loss or something called telogen effluvium - a common form of diffuse, usually temporary hair shedding.

So, why does hair shed more at certain times of year? Can you actually stop hair shedding? And could seasonal changes in light exposure or circadian rhythm have an effect on the hair follicle?

Here's what the science says about seasonal hair shedding, diffuse hair loss and telogen effluvium, plus evidence-based ways to support healthy hair growth.

What is seasonal hair shedding?

Seasonal hair shedding refers to a natural change in the rate of hair shedding that can occur at certain times of year.

The hair follicle moves through a repeating cycle of anagen (growth), catagen (transition), telogen (rest) and exogen (shedding). The proportion of follicles in each stage can shift throughout the year, meaning more hairs may enter the resting phase at certain points before eventually being shed.¹

Research has found evidence of this seasonal pattern in humans. In a long-term study of healthy men in the UK, the proportion of actively growing hairs gradually fell through the summer, reaching its lowest point in September, while hair shedding peaked around August and September.²

Another study involving 823 women found the highest proportion of hairs in the resting, or telogen, phase during summer.³

This may help explain why some people notice increased hair shedding towards the end of summer and into autumn. The precise biological reason is not fully established, although changes in photoperiod - the duration of daylight across the seasons - have been proposed as a possible influence on hair-cycle timing.⁴

Seasonal shedding is a temporary change in the hair-growth cycle and doesn't necessarily indicate progressive hair loss. The pattern also varies between individuals, and increased shedding can have other causes, including illness, stress, hormonal changes, nutritional deficiencies and telogen effluvium.⁵,⁶

Why does hair shed? Understanding the hair growth cycle

Every hair on your scalp is at a slightly different point in its growth cycle. There are four main stages, with the length of time a follicle spends in each stage determining when the hair grows and is eventually shed.¹

(Illustration from iStock showing the four stages of the hair growth cycle) 

Anagen: the growth phase

Anagen is the active growth phase. Cells in the hair follicle divide rapidly, pushing the hair shaft upwards and allowing it to continue growing. Most scalp hairs are in their anagen phase at any given time, and this phase can last for several years.¹

Catagen: the transition phase

Catagen is a short transitional stage. The follicle contracts and hair growth stops as it prepares to enter its resting period.¹

Telogen: the resting phase

During telogen, the follicle rests and the hair is no longer actively growing. This phase typically lasts for several months, while a new hair begins developing beneath the old one.¹

Exogen: the shedding phase

Eventually, the old hair is released from the follicle in a process known as exogen.¹ This is the hair you see in your brush, shower or on your clothes.

Shedding is therefore a normal part of healthy hair biology. The interesting part is what happens when a larger number of follicles enter the resting phase around the same time. That's where telogen effluvium comes in.

Read More: Red Light Caps: Wellness Fad Or Hair Growth Breakthrough?

What is telogen effluvium?

Telogen effluvium is a form of temporary hair shedding that occurs when an unusually large number of hair follicles enter the telogen, or resting, phase at the same time. Because these hairs then progress towards shedding, the result can be a noticeable increase in hair loss across the scalp.⁵,⁶

Unlike pattern hair loss, which typically develops gradually in a specific distribution, telogen effluvium usually causes diffuse hair shedding across the scalp.⁵ The two conditions can coexist, and an episode of telogen effluvium can make previously subtle pattern hair loss more noticeable.⁶

What causes telogen effluvium?

A range of physical or psychological stressors can disrupt the normal hair cycle. These can include:

• A significant illness or high fever
• Major or prolonged stress
• Rapid weight loss or restrictive dieting
• Nutritional deficiencies
• Hormonal changes
• Surgery or other significant physical stress
• Certain medications⁵,⁶

One of the confusing things about telogen effluvium is that the trigger and the shedding don't necessarily happen at the same time. Hair shedding can become noticeable several months after the event that disrupted the hair cycle because follicles don't immediately shed their hair when they enter telogen.⁵,⁶,⁷

In many cases, telogen effluvium is temporary. Once the underlying trigger has resolved and the hair-growth cycle returns to its usual pattern, shedding should gradually decrease.⁶,⁷

Read More: LEDs vs Lasers for Hair Regrowth: What the Science Really Say

Can you stop hair shedding?

There isn't one way to stop hair shedding because the pattern can have different causes. If shedding is linked to a temporary change or trigger, addressing the underlying cause can allow the hair cycle to return to its usual pattern.

There are also simple ways to support healthy hair growth:

• Eat a balanced diet: Adequate protein and micronutrients are important for normal hair biology, while deficiencies in nutrients such as iron can contribute to hair loss. Avoid supplements unless a deficiency has been identified or a healthcare professional recommends them.⁸
• Protect your hair: Limit excessive heat, tight hairstyles and repeated chemical treatments.⁹
• Look after your scalp: Keep it clean and avoid persistent irritation.
• Give it time: Hair grows slowly, so changes won't happen overnight.
• Review possible triggers: A qualified healthcare professional can assess recent illness, surgery, weight change, childbirth, stress, medication changes and symptoms of endocrine or nutritional disorders.

It's also worth remembering that some hair shedding is normal. It's often estimated that people shed around 50–100 hairs a day, although there is considerable individual variation.⁷

Seeing more hair on wash days doesn't necessarily mean you're experiencing hair loss, as several days' worth of naturally shed hairs can come away at once. A clear and sustained change from your usual baseline, however, certainly deserves attention.

Can red light therapy help with hair loss and hair growth?

Research suggests that red light therapy may support hair growth and increase hair density, particularly in people experiencing androgenetic alopecia, also known as pattern hair loss.¹⁰

Low-level light therapy (LLLT), also known as photobiomodulation, has been investigated in multiple randomised controlled trials in the context of pattern hair loss.¹⁰,¹¹

(Photo of the BON CHARGE Red Light Cap) 

A 2025 systematic review and meta-analysis of 38 studies found that low-level laser or LED therapy was associated with increased hair density in people with androgenetic alopecia compared with placebo devices.¹⁰

Earlier reviews have reported similar findings. One meta-analysis of seven double-blind, randomised controlled trials of FDA-approved home-use devices found that LLLT increased hair density compared with sham treatment, with improvements observed in both men and women with pattern hair loss.¹¹

The evidence is less established for other forms of hair loss. The 2025 review included a small number of studies involving conditions such as telogen effluvium, but there wasn't enough data to determine its effectiveness for these conditions.¹⁰

So, while red light therapy shouldn't be presented as a way to stop seasonal hair shedding, there is evidence that specific forms of low-level light therapy can support hair growth and hair density in people experiencing pattern hair loss.¹⁰,¹¹

Read More: 10-Minute Hacks: The Red Light Cap Edition

The BON CHARGE Red Light Cap

The BON CHARGE Red Light Cap is a lightweight, cordless device that delivers targeted 650 nm red light directly to the scalp during pre-set 10-minute sessions.

Designed for convenient, consistent use at home, it supports healthier-looking hair and encourages the appearance of thicker, fuller hair over time.

(Photo of the BON CHARGE Red Light Cap) 

While the cap shouldn’t be presented as a treatment for seasonal shedding or telogen effluvium, it offers a convenient way to incorporate the type of low-level red light therapy investigated in studies of androgenetic alopecia into a regular hair wellness routine.¹⁰,¹¹ Results can vary, and the cap should always be used according to the user manual.

If hair shedding is sudden, severe, persistent or accompanied by other symptoms, speak to a qualified healthcare professional to investigate the underlying cause.

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References

1. Natarelli, N., Gahoonia, N. & Sivamani, R. K. Integrative and mechanistic approach to the hair growth cycle and hair loss. J. Clin. Med. 12, 893 (2023).

2. Randall, V. A. & Ebling, F. J. G. Seasonal changes in human hair growth. Br. J. Dermatol. 124, 146–151 (1991).

3. Kunz, M., Seifert, B. & Trüeb, R. M. Seasonality of hair shedding in healthy women complaining of hair loss. Dermatology 219, 105–110 (2009).

4. Courtois, M., Loussouarn, G., Hourseau, S. & Grollier, J. F. Periodicity in the growth and shedding of hair. Br. J. Dermatol. 134, 47–54 (1996).

5. Rebora, A. Telogen effluvium: a comprehensive review. Clin. Cosmet. Investig. Dermatol. 12, 583–590 (2019).

6. British Association of Dermatologists. Telogen effluvium: patient information leaflet (updated October 2025).

7. American Academy of Dermatology Association. Do you have hair loss or hair shedding? (accessed 25 September 2026).

8. Guo, E. L. & Katta, R. Diet and hair loss: effects of nutrient deficiency and supplement use. Dermatol. Pract. Concept. 7, 1–10 (2017).

9. American Academy of Dermatology Association. Hair styling without damage (accessed 25 September 2026).

10. Perez, S. M., Vattigunta, M., Kelly, C. & Eber, A. Low-level laser and LED therapy in alopecia: a systematic review and meta-analysis. Dermatol. Surg. 51, 179–183 (2025).

11. Lueangarun, S., Visutjindaporn, P., Parcharoen, Y., Jamparuang, P. & Tempark, T. A systematic review and meta-analysis of randomized controlled trials of United States Food and Drug Administration-approved, home-use, low-level light/laser therapy devices for pattern hair loss: device design and technology. J. Clin. Aesthet. Dermatol. 14, E64–E75 (2021).

BON CHARGE: This content is for general education and is not medical advice. Our products are not intended to diagnose, treat, cure, or prevent any disease. Always follow product instructions and consult a qualified healthcare professional for guidance tailored to you. Individual results may vary. -