How a Warming Climate Wears on the Skin

Last summer, as smoke from wildfires in Quebec drifted hundreds of miles to the south, dermatologist Arianne Shadi Kourosh noticed an unusual pattern in her practice at Massachusetts General Hospital: a spike in the number of patients with eczema and dermatitis flares.

“These patients were having bad flares at an unseasonable time of year,” says Kourosh, an HMS associate professor of dermatology at Mass General. “I listened and started to hear a pattern. Then I thought about how to study it.”

Kourosh and colleagues wondered if the uptick could be related to the smoke, which had formed a thick haze over Boston and other cities in the northeastern U.S. Comparing dermatology clinic visits for dermatitis and eczema in the Boston area with carbon monoxide concentrations over several years, they connected the dots. “We confirmed that it’s important to protect the skin when you’re in range of airborne pollution from wildfires and retardants,” Kourosh says, “and we’re only going to see more of these fires as our planet warms.”

As thin as half a millimeter at its most delicate and only a few millimeters deep at its thickest, the skin serves as our main interface with, and protection from, the outside world. Skin lies exposed to our environments and must weather the changes that occur around us, such as seasonal dry air or risk of fungal infection after prolonged rain.

Climate change is compounding the challenge. Skin is “exquisitely sensitive” to climatologic and ecologic shifts, says Louise Andersen, cochair of the International Society of Dermatology Committee on Climate Change and a dermatologist at Aleris-Hamlet Hospitals in Denmark.

“For millennia, our skin has specialized in taking care of environmental challenges, from pathogens to ultraviolet radiation,” she says. “It’s a delicate system where the balance has shifted in recent years.”

Clinicians, researchers, and public health experts at HMS and beyond are sounding the alarm about just how much of a mark our warming, increasingly volatile planet is making on our largest and arguably most vulnerable organ.

The thin cutaneous line

Wildfires are only one of the dangers that climate change poses to the skin.

Ozone depletion, greenhouse gas emissions, and rising temperatures catalyze both atmospheric and behavioral changes that raise individuals’ risk of skin cancers through greater exposure to ultraviolet rays.

Floods from changing rainfall patterns or severe storms carry the threats of chemical exposure, skin injury, fungal infections, and bacterial, viral, and parasitic diseases with skin manifestations. Floodwaters can inflame and irritate the skin, aggravate contact dermatitis, and cause itchy bumps known as prurigo. Even after the waters recede, mold and insects can continue to plague the skin, as researchers have noted after hurricanes such as Katrina, Rita, and Harvey.

Warming climates lengthen allergy seasons, while rising carbon dioxide levels can render plants such as poison ivy more potent. Higher temperatures can also raise the incidence of severe acne and encourage the growth of microorganisms that cause skin disease.

Industrial facilities that produce greenhouse gases pump fine particulates into the air, as do climate-driven wildfires and dust storms. These airborne particles can not only aggravate airway illnesses such as asthma but also land on the skin, exacerbating allergic and irritant dermatitis and eczema.

Climate change also affects the skin indirectly. Whether sparked by a natural disaster or climate migration, stress can both cause and worsen skin conditions such as psoriasis, dermatitis, hives, hair loss, and vitiligo, in which patches of skin lose their pigment, Andersen pointed out in Environment and Skin in 2018.

Although no one can be fully protected from climate change and its threats to the skin, certain populations are at particular risk. Clinicians and researchers worry about people in developing nations, homeless and displaced populations, those with fewer financial resources, and those living in areas with limited health care infrastructure or education. Kourosh collaborates with HMS faculty in primary care and pulmonology to provide environmental protections, such as HEPA filters and mineral sunscreens, to under-resourced residents of Chelsea, Mass.

“Not everyone has the luxury of staying inside with air filters running during acute air pollution events like wildfires,” she says. “It’s important as physicians to be mindful of social barriers that can prevent people from following public health recommendations.”

Under the surface

The skin’s very vulnerabilities, however, offer opportunities. Thanks to their visibility, skin problems can alert clinicians to deeper climate-related health troubles in patients.

“The skin is a viewscreen, a harbinger,” says Kourosh. “What’s happening in the face of climate change and its consequences underscores what we’re always teaching: that paying attention to the skin can reveal internal disease.”

As regional climates shift, for instance, so too do the macroscopic vectors of diseases that can announce themselves on the skin. Consistently warmer weather at higher latitudes and elevations makes more land hospitable to mosquitoes, ticks that transmit Lyme disease, triatomine bugs that carry Chagas disease parasites, and sand flies. Milder winters may kill fewer insect eggs, while earlier springs and later autumns lengthen the season of peak infection. Studies suggest that above-average regional temperatures raise the number of insects within a population that can transmit certain viruses, including mosquitoes carrying chikungunya virus.

Becoming familiar with climate-related skin hazards strengthens health care providers’ ability to treat and even prevent them. Dermatologists have gone further and taken a leading role in climate activism by publishing papers, lobbying governments, and working to make their individual practices more environmentally sustainable. Even before the COVID-19 pandemic popularized telemedicine, some dermatologists embraced the technology for its ability to cut down on carbon-emitting travel while taking advantage of the visual nature of many skin exams.

As global maps of skin diseases morph and spread, investigators, too, have the chance to improve human health, mainly by fleshing out a skeletal body of research. A 2019 review article in the Journal of Toxicology and Environmental Health, Part B highlights one of many specific gaps. In it, a team of HMS assistant and associate professors of emergency medicine at Brigham and Women’s Hospital emphasized the need to collect and analyze data on the toxins and infectious agents in floodwaters following climate-exacerbated “extreme hydrometeorological events.”

When Andersen joined the International Society of Dermatology Committee on Climate Change in 2009, “surprisingly few dermatologists” had paid attention to the possible impact of climate change on skin diseases and “only a few of the many publications describing health impacts of climate change focused on skin disease,” she says.

In the ensuing years, knowledge and engagement have grown. “We’re on the right track, although a lot more work is needed,” Andersen says. “I really do hope that we open our eyes to the problems and try to reverse the changes I see reflected in the skin.”

Stephanie Dutchen is the editorial director in the Office of Communications and External Relations at HMS. 

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