Does Air Pollution Cause Hair Thinning? What the Evidence Shows So Far

Search for haze and hair during any haze season and the headlines arrive quickly, and many are more certain than the research behind them. If you have just noticed thinning in the mirror, that certainty can land hard.

The evidence is worth reading at its actual size. Here is how far it goes, and where it stops.

What has laboratory work shown?

Early laboratory work, on hair follicle cells grown in dishes and on animals, suggests that fine particles can stress and irritate the cells involved in producing hair. That is a plausible route, and it is why researchers took the question to human populations.

It is also where laboratory work reaches its limit. Cells in a dish receive particles under conditions chosen by the experimenter, which is very different from a living scalp in a city. These studies show that a mechanism is possible. They do not show that pollution thins hair in people.

What does the main human study on thinning show?

For the common, gradual kind of thinning, the only large human study so far is a Korean research letter (Park and colleagues, 2026). Researchers used national health-insurance records for 5,591,500 adults and estimated each person’s long-term exposure to fine particles from their home address. Over a median follow-up of about twelve and a half years, 5,179 people received a diagnosis of that kind of thinning, roughly one in a thousand.

Higher long-term exposure went with a higher rate of diagnosis. For each 10 µg/m³ rise in long-term PM2.5, the hazard ratio was 1.61 in men and 1.11 in women: a stronger association in men.

The limits are as important as the numbers.

• It shows an association. That alone cannot establish cause: people in more polluted areas differ in many ways, including how often they see a doctor and are given a diagnosis code.
• The authors themselves raise an alternative. They allow that particles might provoke a general inflammation that only resembles hereditary thinning, which would be a different process altogether.
• It is early and has not been replicated. It is one study, from one country and one research group, published as a one-page letter.
• It counts diagnoses. People who did not seek care are invisible to it, and early thinning of the kind most readers notice first is not what was measured.

What do the skin studies in Singapore and the UK add?

They are often quoted alongside the hair question, but they answer a different one. A nationwide Singapore study (Mailepessov and colleagues, 2024; 1,440,844 consultations) and a large UK cohort (Chen and colleagues, 2024; 193,995 adults) both link higher air-pollution exposure with more inflamed skin conditions. They measured skin inflammation. Neither measured hair. Their details are set out in haze season and your scalp.

For context on confidence, a systematic review of 77 epidemiological studies on air pollution and skin conditions (Singh, Schikowski and Krutmann, 2026) found that most pointed towards harm, yet rated the certainty of the evidence usually low to very low because of a high risk of bias. That review did not cover the scalp or hair at all.

Has any product been shown to help?

No. No human study shows that any shampoo, tonic, serum or scalp product reduces pollution-related thinning. Washing removes particles, sweat and oil from the scalp surface, which is sensible hygiene and the subject of your scalp is skin. It has not been tested as a way to change thinning.

What about Malaysia?

There is no Malaysian study of haze and skin, scalp or hair. No study anywhere has examined peat-fire smoke, the main source of the region’s seasonal haze, in relation to hair. The Korean hazard ratios describe Korean adults and Korean air over a particular period; they cannot be scaled onto Malaysia.

What does a careful person do with this?

Hold two things at once. The question is legitimate, and serious researchers are working on it. The answer, so far, is unknown.

In practice, that points to ordinary care rather than alarm. Keep the scalp clean and comfortable, especially through haze weeks, as set out in haze season and your scalp. Watch the signals that matter more than any headline: a sustained change from your usual pattern, a part that keeps widening, or distinct patches. How much daily shedding is normal explains how to record change sensibly, and hair breakage versus shedding helps separate a fibre problem from a scalp one.

And if your density is changing, pollution research cannot tell you why. A doctor can assess the many known causes of shedding and thinning, among them illness, childbirth, substantial weight change, some medicines and inherited patterns, and an assessment is how the cause is found.

When should you see a doctor?

Haircare cannot address a medical cause of thinning. Shampoos, conditioners and scalp products work on the scalp surface and on the hair itself; they do not identify a cause and they do not replace an assessment. See a doctor for sudden or marked shedding, smooth or bare patches, a part that keeps widening, scalp pain, redness or scaling that does not settle, loss of brows or lashes, or any change that continues for several months. Bring a note of when it began and what happened in the months before, together with a list of any medicines or supplements you take.

Conclusion: a plausible link, not yet an established one

Laboratory work makes a connection between fine particles and thinning plausible, and one large Korean study found an association. Neither shows cause, nothing has been tested in Malaysia, and no product has been shown to change the outcome. Care for the scalp as the skin it is, and take any sustained change in density to a doctor.

Sources and further reading

• Park et al. (2026), JAAD International: long-term particulate matter exposure, Korean nationwide cohort of 5,591,500 adults
• Singh, Schikowski and Krutmann (2026), American Journal of Clinical Dermatology: air pollution and skin conditions, a systematic review of 77 studies
• Mailepessov et al. (2024), Scientific Reports: ambient air pollution and skin consultations in Singapore
• Chen et al. (2024), Clinical and Experimental Dermatology: air pollution and new skin diagnoses in a UK cohort of 193,995 adults
• Haze season and your scalp
• Your scalp is skin: what that changes every time you wash
• How much daily hair shedding is normal?
• Hair breakage versus shedding