LONG-TERM exposure to particulate matter (PM) may increase the risk of developing alopecia areata (AA), according to a large nationwide epidemiological study.
Researchers investigated whether chronic exposure to fine particulate matter (PM2.5) and coarse particulate matter (PM10) was associated with new cases of AA, an autoimmune condition characterised by patchy hair loss. The study linked annual average PM exposure data with national health screening records from individuals followed between 2006 and 2022.
Incident AA was identified through healthcare records, with cases defined as patients having at least three outpatient claims with relevant diagnostic codes within one year.
PM2.5 and PM10 Exposure Linked to Increased Alopecia Areata Risk
Higher exposure to both PM2.5 and PM10 was associated with a significantly increased risk of developing AA. For every 10 μg/m³ increase in PM2.5 exposure, the risk of AA increased by 45% (adjusted hazard ratio [HR] 1.45), while a similar increase in PM10 exposure was linked to a 32% higher risk (adjusted HR 1.32).
The strongest association was observed in patients with alopecia universalis, the most severe form of AA involving loss of hair across the scalp and body. A 10 μg/m³ increase in PM2.5 exposure was associated with more than double the risk of alopecia universalis (adjusted HR 2.23), while PM10 exposure increased risk by 82% (adjusted HR 1.82).
To explore possible mechanisms, the researchers also conducted laboratory experiments using human hair outer root sheath cells exposed to PM10-like fine dust for 24 hours. Exposure increased the production of reactive oxygen species and triggered inflammatory responses, including increased expression of cytokines involved in immune activation, such as IL-1β, IL-6, IL-8 and IL-15RA. PM exposure also activated inflammatory signalling pathways involving p38 and STAT3.
The authors suggest that air pollution may represent a modifiable environmental risk factor for AA by promoting oxidative stress and inflammation in hair follicle-related cells.
Reducing Particulate Matter Exposure May Represent a Future Prevention Strategy
The findings highlight the potential importance of reducing particulate matter exposure as part of broader public health strategies and may provide new insights into environmental contributors to autoimmune hair loss. Further research is needed to confirm causality and determine whether reducing pollution exposure can lower AA risk.
Reference
Kim M et al. Long-term particulate matter exposure and risk of alopecia areata: a nationwide epidemiological study with preliminary in vitro evidence. Br J Dermatol. 2026; DOI: 10.1093/bjd/ljag254.
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