Due to their small size, fine particulate matter can penetrate deep into the lungs and potentially even cross the skin barrier. Several studies suggest that PM2.5 may contribute to the development or worsening of eczema through several mechanisms, including oxidative stress, skin barrier damage, and aryl hydrocarbon receptor activation.
A large US cross-sectional study has now examined the extent to which particulate matter exposure is associated with eczema in adults. Data from approximately 287,000 adults were analyzed, including 12,695 people with medically diagnosed eczema.
The results show a statistically significant difference in particulate matter exposure: eczema patients lived, on average, in areas with higher PM2.5 concentrations (8.3 vs. 8.1 μg/m³). Despite this small mean difference, the result was highly significant (p < 0.001) due to the large sample size.
Various statistical models confirmed that the risk of eczema increases with increasing particulate matter exposure: Without considering other factors, the odds ratio (OR) was approximately 1.97 per 10 μg/m³ increase in particulate matter. When additional influencing factors such as age, gender, ethnicity, urbanity, income, BMI, and smoking status were taken into account, the risk increased to approximately 2.6. When the presence of other atopic diseases (such as asthma, allergic rhinitis, or food allergies) was also taken into account, the result changed only slightly (OR ~2.66).
In other words: people in areas with higher particulate matter exposure were approximately two to two and a half times more likely to suffer from eczema compared to people in areas with lower exposure. It is particularly noteworthy that this effect was observed regardless of existing allergies or smoking status. Therefore, particulate matter appears to be an independent risk factor for eczema.
The results from the US study are consistent with findings from other parts of the world. In Taiwan, for example, a 1.63-fold increased risk of eczema was observed for every 10 μg/m³ increase in particulate matter. A German study of older women showed a comparable risk (OR ~2.2 per 10 μg/m³). Australian researchers also reported a significant association of particulate matter with atopy (OR ~2.4 per 10 μg/m³).
Despite different populations and methodologies, all of these studies consistently indicate that increased particulate matter exposure is associated with approximately a doubling of the risk of eczema. The current US study further supports this association with its large and diverse sample.
The results suggest that fine dust is an important environmental risk factor for eczema. From a dermatological perspective, this underscores the importance of air quality for skin health. While a cross-sectional study cannot establish a clear causal relationship, fine dust appears to be a modifiable factor that could be usefully addressed through preventive measures. Measures to reduce fine dust pollution—whether through targeted environmental policies or individual protective measures—could therefore make an important contribution to the prevention of inflammatory skin diseases.