Air pollutants such as nitrogen dioxide (NO2), carbon monoxide (CO), sulfur dioxide (SO2), and ozone (O3) are linked to the prevalence and severity of atopic dermatitis. These contaminants have been linked to an increased risk of AD during pregnancy, childhood, and maturity.
Atopic dermatitis (AD) is a chronic, inflammatory skin disease affecting approximately 20% of children and 3% of adults worldwide. Increasing evidence indicates air pollution is a risk factor for AD development in susceptible individuals.
A study in Clinical Reviews in Allergy & Immunology reviewed the relevant research to assess the association between air pollution and AD.
Mechanistic Linkage of Air Pollution and AD
The two main pathophysiological mechanisms in AD are impaired skin barrier and immune dysregulation. Air pollutants may lead to skin barrier impairment through increased oxidative stress, water loss, physiochemical injury, and changes in microflora. Moreover, oxidative stress can induce immune dysregulation, increasing sensitization to allergens.
Gases Linked to Atopic Dermatitis Severity
Nitrogen dioxide (NO2) has a significant association with the prevalence of AD, as established by extensive research. Several studies have also demonstrated its association with disease severity. Studies during pregnancy and infancy have shown a positive correlation of NO2 with AD and first-trimester exposure with infant AD. However, one study found no correlation throughout pregnancy or three months after birth.
Studies have shown the association of carbon monoxide (CO) and nitrogen oxides (NOx) with both lifetime and past-year risk of AD. An adult cohort study linked NOx to AD incidence.
Higher annual CO levels are associated with higher infantile AD prevalence. Studies demonstrate a correlation between CO and AD, but conclusions for other gases vary. In a large national study, sulfur dioxide (SO2) and CO were found to be risk factors for AD. Another large study linked acute NO2, SO2, and O3 exposure to increased hospital visits for AD.
Mixed Air Pollutants and Atopic Dermatitis
Studies have positively correlated particulate matter (PM) levels to AD prevalence. AD patients showed greater potential PM exposure than those without AD, and higher PM levels were significantly associated with increased outpatient visits for AD. Several studies on AD patients demonstrated a correlation between worsening itch and rising ambient PM concentration. Overall, more studies support the role of PM than single gases in AD development.
Proximity to Busy Roads Increases Childhood Atopic Dermatitis Risk
Research regarding traffic-related air pollution has shown that children living closer than 50 m from a busy road or street displayed higher AD prevalence than those living farther away. One study found that shorter living distance to a main road during pregnancy was associated with an increased risk of infant AD. Other studies also link AD prevalence and severity to road proximity and vehicle density.
Outdoor Volatile Organic Compound Concentration Correlates With Childhood Atopic Dermatitis
A large cross-sectional study in children found a positive correlation between outdoor volatile organic compound (VOC) concentration and recent AD. Multiple studies on indoor VOCs show varied results. Indoor renovations in the last 5 years were linked to AD severity. Another study found no correlation between VOC exposure in pregnancy and infancy to AD, but a positive correlation with inflammatory cytokines was noted. Organophosphate esters, hydrocarbons, butyl benzyl phthalate, formaldehyde, propylene glycol, and glycol ethers were also found related to AD in various studies, as were mosquito coils and new furniture.
Tobacco Smoking Linked to Higher Risk of Adolescent Atopic Dermatitis
Both active and passive tobacco smoking positively correlates with AD in adolescents. Individuals with AD were more likely to have smoking exposure at home than those without the disease. Studies also linked second-hand smoke exposure and prenatal exposure to higher AD risk. Smoking pack-year was found to be significantly related to adult-onset AD.
Studies on the effects of bioaerosols on AD are limited and inconclusive. The available evidence suggests a positive correlation of the disease with total fungal spores in males and butyl benzyl phthalate from floor dust in children.
Pan, Z., Dai, Y., Akar-Ghibril, N., Simpson, J., Ren, H., Zhang, L., Hou, Y., Wen, X., Chang, C., Tang, R., & Sun, J. (2023). Impact of air pollution on atopic dermatitis: A Comprehensive review. Clinical Reviews in Allergy & Immunology. https://doi.org/10.1007/s12016-022-08957-7