Eighteen studies with evidence on the impacts of climate change on atopic dermatitis (AD) have been highlighted in a new analysis, with climatic hazards affecting eczema comprising direct effects such as particulate matter-induced exacerbations resulting from wildfires or indirect effects such as drought-induced food insecurity.¹

These findings and more were highlighted in this analysis of atopic dermatitis and its connection to changes in the Earth’s climate primarily due to manmade conditions. The research was led by Katrina Abuabara, MD, from the department of dermatology at the University of California San Francisco in California.

In addition to looking at hazards, data, and research gaps, Abuabara and colleagues created maps designed to compare the past, present, and future projected burden of climatic issues to global prevalence of eczema. For the purposes of this summary, eczema and atopic dermatitis are used interchangeably.

“Although AD frequently presents in childhood, it may resolve, persist, or first present in adulthood,” Abuabara and colleagues wrote. “It is important to understand the current and potential future impact of climate change on AD because environmental factors have been repeatedly shown to influence disease onset and course.”^2,3

Background and Findings

The investigators identified several studies in which they pointed out environmental factors impacting atopic dermatitis, some of which were toxins, UV radiation, temperature, environmental allergens, and humidity. The "brick and mortar" model, the research team noted, highlights the skin barrier's structure, which, when it is impacted by elements such as UV exposure, variations in temperature, and toxins, can result in inflammation and dysfunction in the skin barrier.

For patients known to have atopic dermatitis, susceptibility to environmental factors is shown by the team’s research to be heightened as a result of immune dysregulation, skin barrier impairment, cutaneous dysbiosis, and chronic itch, establishing a cycle that perpetuates the skin disease.

The research team systematically screened different studies for ones which connected climatic hazards linked to greenhouse gas emissions with eczema, excluding studies that did not have primary data directly assessing such an association. The search was done in April 2023 across Embase, PubMed, and Google Scholar.

The team looked into the location of the condition, age group, disease outcome, different mechanisms, and impacts, creating maps designed to depict the Cumulative Climate Hazard Index (CCHI) relative to prevalence of atopic dermatitis through the use of Global Burden of Disease data.

Overall, the investigators sought to highlight the co-occurrence of climatic hazards around the world, comparing global cumulative exposure in the year 2005 with the following decade's estimated eczema prevalence shifts. They also compared 2017’s data on cumulative exposure with 2017 prevalence of eczema and projected 2053 exposure based upon current practices.

From the 18 studies assessed by the research team, data had been collected in 10 countries. The team’s analysis of 18 studies indicated that global warming could exacerbate atopic dermatitis conditions through mechanisms such as increased temperature-induced pruritus, proinflammatory cytokines, and changes in the presence of aeroallergens.

Conflicting results were also noted by the investigators, with some of the research linking higher temperature to heightened severity of the skin disease and heightened prevalence. Despite this fact, others indicated a decrease in such effects.

Extreme weather events and heat waves, specifically, were highlighted by the research team as inducers of psychological and physical stress in those with and without the condition, leading to potential exacerbations. They did note, however, that specific studies on heat waves and links with eczema were not observed.

The investigators also looked at the effect of wildfires on patients, noting their impacts on oxidative stress exacerbations and the harm of air pollution being elevators as far as clinic visits for eczema. This was especially seen among younger and older individuals. The team added that drought was indirectly linked to atopic dermatitis, given its impact on health care and contributions to other hazards such as wildfire occurrence.

The research team also highlighted the complexity of precipitation's observed impact on eczema, as studies suggested mixed results. Sea level rises, storms, flooding, and ocean climate change were acknowledged by the team as indirectly impacting patients through various mechanisms, though evidence was shown to be limited.

The investigators added that land cover change, specifically in urban regions, was not shown to have strongly been linked to eczema prevalence based upon the available research.

When looking at prevalence estimates for the future, the research team reported that if current trends in greenhouse gas emissions persist, the severity of hazards in the climate were projected to substantially increase by the year 2053 (CCHI range: 0.24 to 4.18), compared to the year 2017 (CCHI range: 0.01–2.65).

The team added that in 2017, Africa, Southeast Asia, and Central America, especially in the coastal regions of these locations, were shown to have major cumulative climatic hazards. Although Africa and Central America had been shown to have lower prevalence of the skin disease, Southeast Asia was found to have a prevalence above the median.

The investigators noted that such tropical regions, particularly the coastal regions, are predicted to face some of the most impactful effects of climatic hazards in 2053.

“Our study adds to the research on climate change by providing clarity about the extent of research on climatic hazards and AD, including the research gaps and lack of evidence in the locations most impacted now and projected to be most impacted in the future,” they wrote.

References

1. ^{Wang S-P, Stefanovic N, Orfali RL, et al. Impact of climate change on atopic dermatitis: A review by the International Eczema Council. Allergy. 2024; 00: 1-15. doi:10.1111/all.16007.}
2. ^{Abuabara K, Langan SM. Atopic dermatitis across the life course. Br J Dermatol. 2023; 188(6): 709-717.}
3. ^{Stefanovic N, Flohr C, Irvine AD. The exposome in atopic dermatitis. Allergy. 2020; 75(1): 63-74.}