Exposure to air pollution has been linked to an increased odds of eczema in adult males and increased aeroallergen sensitisation in both men and women.

The study of more than 3,000 participants from the Tasmanian Longitudinal Health Study comprised a postal survey of participants at age 43 years and comprehensive follow-up including skin prick tests at 53 years.

The residential address of participants allowed for calculations of distance to a major road, ambient NO₂ levels and fine particulate matter (PM_2.5).

The study found 8.96% of the participants had prevalent eczema at 53 years of age, 3.67% had incident eczema, and 6.38% had persistent eczema.

It found that higher baseline exposure to NO₂ was associated with increased odds of having prevalent eczema at follow-up in males (adjusted odds ratio (aOR):1.15) while higher exposure in females had non-significant, reduced odds of prevalent eczema (aOR:0.83).

Similarly, in males, baseline NO₂ exposure was associated with increased odds of having sensitisation to at least one of eight aeroallergens (aOR 1.26 [1.00- 1.59]) per 2.27 ppb NO₂ increase, while baseline PM_2.5 was associated with increased odds of having aeroallergen sensitisation (aOR 1.47 [1.04-2.06]) per 1.56 μg/m³ PM_2.5 increase.

“By contrast, in females, higher NO₂ exposure at baseline was associated with a reduced odds of having atopic eczema (AE) (aOR0.65 [95% CI 0.43-0.99]) per 2.27 ppb NO₂ increase. A similar trend was seen at follow-up, NO₂ was associated with a reduced odds of AE (aOR0.67 [0.44-1.01]) per 2.21 ppb increase.”

The study authors said their findings of an association between PM_2.5 and aeroallergen sensitisation were consistent with other studies.

“Our results support an effect of ambient air pollution on immune function, even in this low ambient air pollution setting,” they said. “Ongoing efforts to reduce ambient air pollution exposure are likely to have a range of health benefits.”

Senior investigator on the study Associate Professor Adrian Lowe, told the limbic the idea that pollution might be impacting the skin was quite plausible given the skin was in contact with the external environment all the time.

“We know that pollution causes oxidative stress and oxidative stress could be breaking down that important barrier that the skin is providing and resulting in symptoms like eczema and rash.”

Associate Professor Lowe, an NHMRC Career Development Fellow and deputy leader of the Allergy and Lung Health Unit at the University of Melbourne, said the sex-specific effects of air pollution could not yet be explained.

“It is intriguing. Men and women are quite different in both our behaviour, for example in regards to sun exposure and how we interact with the outdoor world, but also in how we treat our skin. Males are generally less likely to engage in skin care routine and maybe the things we are doing make us more susceptible to the impacts of pollution.”

He said eczema in adults was understudied.

“We also want to study whether or not some of these genetic risk factors change the effect of pollution on the development of eczema. So, are some of these people with filaggrin mutations more likely to develop eczema if they are in a high pollution environment?”

“That may impact on recommendations for where people with genetic risk factors might live.”

“We are at a point in history where we are moving away from burning fossil fuels and it does look like that is going to have a range of benefits for us. But for the people who are suffering from eczema or who can’t really choose how far from major roads they are living, we can’t at the moment translate these results into concrete actions.”