This Is Eczema on Air Pollution
Exposure to toxins like wildfire smoke can leave you vulnerable to skin irritation.
For 17 harrowing days in November 2018, the deadliest wildfire in the California’s history swept across the northern region of the state. Officially dubbed the Camp Fire (named after its origin point at Camp Creek Road in Butte County), the fire continued to spread for several weeks, capturing national attention. Scientists and environmental experts recognized it as a sign of the increasing impacts of climate change on the West Coast wildfire season: As global temperatures rise, California’s already fire-prone landscape becomes more susceptible to dangerous blazes with each passing year.
For locals, the Camp Fire’s effects have long outlasted that initial media frenzy. Three years later, and many Californians are still working to rebuild their homes and lives. But disasters like this permeate deeper than the immediate economic damage—they also have a long-term impact on human health. A new study in JAMA Dermatology has found that wildfire smoke may trigger and exacerbate eczema symptoms, even in people with no known history of chronic skin disease.
Researchers at the University of California San Francisco collected data from dermatology visits by 4,147 people who lived in San Francisco, approximately 175 miles from the source of the Camp Fire. During the weeks when wildfire-related air pollution was highest, they discovered a significant increase in doctors’ visits related to atopic dermatitis (a.k.a. eczema) or itch. It wasn’t just people with pre-existing eczema who developed symptoms during the wildfire, but also people who had never reported these symptoms before.
These findings illustrate one of many ways that air pollution, worsened by climate change, can aggravate (or induce) skin barrier dysfunction. “Generally, conversations about climate change policy, mitigation, and prevention haven’t considered the effects of air pollution from wildfires on skin health,” says Raj Fadadu, environmental epigenetics graduate student researcher at University of California San Francisco (UCSF) and first author of this study. “Perhaps these [skin] diseases should be discussed more when thinking about the many ways in which the changing climate impacts human health.”
Unlocking the Cause(s) of Eczema
One of the challenges in studying eczema is that it’s an extremely complicated health condition, and the origin and risk factors vary from person to person. Eczema (or atopic dermatitis, as it is formally known) is believed to be caused by a combination of genetics and environmental factors, both of which can compound to make symptoms worse. For instance, someone might be born with an overactive immune system (genetics), which is then triggered by external irritants like cigarette smoke or household cleaners (environment), causing an eczema flare.
“The skin is a wonderful barrier—that’s its function,” explains Maria Wei, M.D., professor of dermatology at UCSF and co-author of the wildfire study. “It is a barrier against physical entities, gases, liquids, infections, and temperature [changes]. But it does have its limits, and there are ways for components of pollution to breach that barrier”—especially when the skin barrier is already in a compromised state.
How Air Pollution Harms Your Skin
Exposure to pollutants contributes to eczema in several ways: oxidative stress, skin barrier dysfunction, immune stimulation, and exacerbation of itching and scratching. And different types of pollution—car exhaust, construction zones, cigarette smoke—likely have somewhat different impacts on the skin. But here’s what we know: “They all seem to have a very strong pro-oxidative effect,” explains Raj Chovatiya, M.D., a dermatologist with Northwestern Medicine in Chicago.
These pollutants cause damage to the skin and deplete its natural antioxidant mechanisms. In addition, Dr. Chovatiya says, “they can mess around with the normal skin microbiome,” changing the balance of healthy cells that keeps your skin barrier strong and protective against infection. All of this, combined with the stimulation of your body’s immune response, contributes to skin irritation and eczema symptoms, and it may even trigger new symptoms in people with underlying skin sensitivity.
We know that chemical-based cleaning products (especially those with harsh ingredients or fragrances) can provoke eczema symptoms, so it makes sense that outdoor pollutants would be able to do this, too. But one major challenge researchers face is trying to sort out the specific impacts of air pollution on skin health. “This is a very difficult kind of study to do in isolation,” Dr. Chovatiya notes.
After all, it’s not like you can pick out individual air pollutants and expose people to them in a laboratory setting. “We know there are a lot of different environmental factors that influence eczema,” he says. “Even aside from pollution, you’re talking about UV light, precipitation, humidity, temperature, and other environmental factors.”
So, what we see in the research is more of a case for correlation, not causation—there’s a link between eczema and air pollution, but it’s not clear exactly how strong that link is or who is most at risk. One review in Clinical Reviews in Allergy & Immunology examined the effects of man-made outdoor pollutants like vehicle exhaust, tobacco smoke, and particulate matter on atopic dermatitis. The authors found strong evidence of a connection but emphasized the need for further research to better understand the specifics.
A 2019 literature review in the British Journal of Dermatology noted that while air pollutants pose a “multifaceted threat” to atopic dermatitis, the specific mechanism through which this happens is not totally clear. Similarly, this wildfire study revealed an association between wildfire pollution exposure and eczema symptoms, but the authors were not able to definitively name it as the primary cause.
Still, Dr. Chovatiya notes, the growing research on this topic is becoming more and more compelling. With the wildfire study, “we have yet another piece of evidence to suggest that in addition to having negative impacts on the global environment, [air pollution] actually has a negative impact on health,” he says. And targeting air pollution may be one way to slow the increase in eczema cases across the world.
The Big-Picture Impact
The estimated prevalence of eczema has more than doubled in the past 30 years, especially in urban areas and industrialized countries. “The rising prevalence of atopic dermatitis in industrialized countries globally is coincident with urbanization, industrialization, and consideration of the impact of air pollution on the development and course of atopic dermatitis,” says Lawrence Eichenfield, M.D., professor of dermatology and pediatrics at UC San Diego School of Medicine and chair of the National Eczema Association’s Scientific and Medical Advisory Council.
Air pollution is on the decline in some affluent countries, including the United States, yet 55% of the world’s population (mostly those in mid- to low-income countries) are being exposed to increasing levels of air pollution year after year. And although the air quality is improving here, it’s still far from where it needs to be: the Environmental Protection Agency (EPA) estimates that 97 million Americans lived in counties with pollution levels exceeding national air quality standards in 2020.
“Both short term and long-term exposure to pollutants may exacerbate symptoms of atopic dermatitis,” Dr. Eichenfield notes. This could be a key factor to help explain the vast upswing in atopic dermatitis diagnoses, especially in highly industrialized places with minimal environmental regulations.
So, what’s next, and how do we begin to solve this global issue? Dr. Chovatiya hopes that future research will help distinguish the causes of eczema on a more individualized level—including the way that air pollution may damage the skin. “Maybe air pollution doesn’t matter to every single person with eczema,” he considers. “Who is going to be that person who is most affected by a forest fire, a high industrial area, or a construction site?” This information would allow doctors to help patients craft a treatment plan that targets their specific needs.
For now, people with eczema can continue to stick to the generalized prevention guidance: avoid exposure to harsh chemicals, allergens, and fragrances. “Being aware of pollution levels on a day-to-day basis is important,” too, Dr. Eichenfield suggests, “and minimizing outside time during bad pollution days is a reasonable strategy.”
If you’re hoping to broaden your impact and get involved in advocacy work, environmental groups like Earthjustice and the American Lung Association have clean air campaigns with opportunities for volunteers.
This conversation will remain relevant as we continue to see the impacts of environmental devastation caused by climate change. Fadudu hopes that the UCSF wildfire study can add one more piece to the puzzle of understanding climate change and public health. “Not only can there be greater public health skin-related education for communities affected by wildfires,” he says, “but we can also use these results to show that wildfire smoke and air pollution affect people’s and communities’ skin health, which can impact quality of life.” We all deserve access to clean natural spaces, for ourselves, our children, and the generations ahead.
Wildfire Study: JAMA Dermatology. (2021.) “Association of Wildfire Air Pollution and Health Care Use for Atopic Dermatitis and Itch.” https://jamanetwork.com/journals/jamadermatology/article-abstract/2778632
Increasing Air Pollution: npj Climate and Atmospheric Science. (2020.) “Half the world’s population are exposed to increasing air pollution.” https://www.nature.com/articles/s41612-020-0124-2
Air Pollution Global Data: World Health Organization. (n.d.) “Air pollution.” https://www.who.int/health-topics/air-pollution
U.S. Air Quality: United States Environmental Protection Agency. (2020.) “Air Quality—National Summary.” epa.gov/air-trends/air-quality-national-summary
Climate Change & Fire Season: Environmental Research Letters. (2020.) “Climate change is increasing the likelihood of extreme autumn wildfire conditions across California.” https://iopscience.iop.org/article/10.1088/1748-9326/ab83a7
Eczema & Environmental Triggers: National Eczema Foundation. (2020.) “The impact of the envirome on eczema.” https://nationaleczema.org/envirome-research/
Oxidative Stress: Oxidative Medicine and Cellular Longevity. (2014.) “Oxidative Stress and Diseases: Clinical Trials and Approaches.” https://www.hindawi.com/journals/omcl/2016/2721469/
Chemical Exposure & Eczema: Toxicological Research. (2015.) “Influences of Environmental Chemicals on Atopic Dermatitis.” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4505354/
Air Pollution & Eczema: British Journal of Dermatology. (2019.) “The impact of airborne pollution on atopic dermatitis: a literature review.” https://onlinelibrary.wiley.com/doi/abs/10.1111/bjd.18781
Outdoor Pollutants: Journal of Allergy and Clinical Immunology. (2014.) “The role of air pollutants in atopic dermatitis.” https://www.jacionline.org/article/S0091-6749(14)01357-8/pdf
Eczema Prevention: National Institute of Allergy and Infectious Diseases. (n.d.) “Eczema (Atopic Dermatitis) Causes & Strategies for Prevention.” https://www.niaid.nih.gov/diseases-conditions/eczema-causes-prevention-strategies