Why You're Losing More Hair in Summer (And What to Do About It)

If you’ve noticed more hair on your pillow or in the shower drain toward the end of summer, you’re not imagining it. And no — it doesn’t necessarily mean something is wrong. But it does mean something happened a few months earlier that you may not have paid much attention to.

Here’s what’s actually going on, and what you can do about it.

Hair grows in cycles. Each follicle moves through three phases: anagen (active growth), catagen (transition), and telogen (resting, followed by shedding). At any given time, roughly 85–90% of your hair is in the anagen phase, meaning actively growing, with the rest in a resting state.

According to research, the proportion of hairs in the telogen phase peaks in late summer, particularly in July and August. More follicles than usual enter the resting phase simultaneously during this period, which then leads to noticeable shedding that follows several weeks later, often landing squarely in September and October.

This is sometimes called seasonal telogen effluvium: a temporary, physiologically-driven increase in shedding that follows a period of stress on the follicle. Summer, with its UV exposure, heat, humidity, and sweat, delivers quite a bit of that stress to the scalp. In many cases, the shedding you see in fall is the delayed result of what your scalp went through during the summer months.

When people think of UV damage, they think mostly about its impact on the skin. But UV radiation doesn’t stop at the surface of the scalp — it penetrates into the tissue and reaches the hair follicle itself.

Research published in the International Journal of Cosmetic Science demonstrated that UV radiation (both UVA and UVB) triggers cytotoxicity and oxidative DNA damage in hair follicles. In plain terms: UV creates cellular stress that disrupts normal follicle function. It does this through reactive oxygen species — those unstable molecules generated in the skin under UV exposure that damage cellular structures, including the DNA and proteins inside the follicle.

Studies have also noted that individuals with repeated, significant UV exposure on the scalp experienced reduced follicle thickness and changes in the supportive connective tissue around follicles. The scalp isn’t just a surface to cover: it’s a living tissue housing your hair follicles, and it deserves the same thoughtful protection you give your face.

Your scalp has a skin barrier that keeps moisture in and irritants out, just like the rest of your body. Summer stresses it in a specific way.

Heat increases oil production. Add sweat, humidity, and product residue, and you create conditions where the follicle opening can become partially congested. When bacteria accumulate in this environment, it can lead to folliculitis — inflammation of the hair follicle — or low-grade scalp congestion that quietly disrupts the follicle’s growth cycle.

This matters because chronic, low-grade scalp inflammation is now recognized as a contributing factor in hair thinning, even when it doesn’t feel overtly irritated. The scalp doesn’t have to be visibly red or itchy to be affecting your follicles underneath. Supporting a clean, balanced scalp environment during the warmer months is one of the more practical things you can do for your hair and scalp.

Then there’s regular summer swimming. It’s a lot of fun, but it’s worth taking a closer look at what the chlorine in pool water actually does to your scalp and hair.

Chlorine, at the concentrations used in pools, strips the natural oils that coat the hair shaft and scalp, lifts and roughens the cuticle (the outer protective layer of each hair strand), and increases hair porosity. High-porosity hair loses moisture faster, becomes brittle, and breaks more easily. That breakage can look and feel like thinning even when the follicle itself is functioning normally.

What chlorine generally doesn’t do, based on current evidence, is directly trigger androgenetic (genetic pattern) hair loss or cause lasting follicle damage in most healthy people. The concern is structural damage to the hair shaft, which is real and worth addressing, especially with repeated exposure.

Rinsing your scalp and hair with clean water before swimming so they absorb less chlorinated water in the first place would help. Wearing a swim cap reduces direct chlorine contact further, though it’s not perfect. 

After swimming, rinse scalp and hair thoroughly with clean water as soon as possible, then follow up with a gentle, non-stripping shampoo, like our Daily Shampoo, to clear any residue without compounding the dryness. A scalp and hair-nourishing product, like our Hair Treatment and Hair Essence, afterward (something with humectants or soothing ingredients like panthenol or allantoin) can help replenish what the chlorine stripped away. If you swim often, doing this consistently after each session matters more than any single treatment.

The seasonal stressors during summer — UV, heat, sweat, and chlorine — share a common underlying problem: they make the scalp a less hospitable environment for healthy follicle function. The response isn’t to layer on more products. It’s to consistently support the scalp’s own ability to stay balanced and resilient.

A few things that matter:

• Gentle, regular cleansing. Sweat and sebum should be cleared consistently, but without stripping the scalp. A mild shampoo that cleanses without disrupting the scalp barrier lets the follicle environment stay balanced.
• Scalp-focused nourishment. The hair strand itself is dead tissue. The follicle, which is where hair is actually formed, is alive, and it responds to what the scalp receives topically. Products containing ingredients like Panax ginseng extract (shown to support microcirculation in the scalp), biotin, and amino acid complexes work at this level: supporting the follicle rather than just coating the strand.
• Consistency over intensity. One scalp treatment in September won’t undo three months of UV exposure and follicle stress. Building scalp support into your regular routine before the stress accumulates is what makes the difference.