How Wildfire Smoke Triggers Allergic Disease Long After It Clears

This summer, smoke from Canadian wildfires drifted south, casting East Coast and Midwest skies in a murky orange-yellow haze and putting millions at risk of respiratory and cardiovascular harm.¹

Numerous states experienced "very unhealthy" or "hazardous" air quality ratings.¹ The polluted air led to widespread event cancellations, including a baby parade in Michigan, a rock concert in Virginia, and the America's Mile marathon in Pittsburgh. According to CNN, Detroit, Milwaukee, Chicago, southern Ohio, and West Virginia recorded the worst air quality in the country.¹

Detroit ranked as the city with the worst air quality in the world, according to IQAir. At an air quality index (AQI) of 724, this was more than double the threshold for the "hazardous" category.1

Simply standing on a front porch and inhaling minuscule smoke particles can trigger coughing, trouble breathing, wheezing, asthma attacks, stinging eyes, a scratchy throat, a runny nose, irritated sinuses, headaches, fatigue, chest pain, and a rapid heartbeat.³ While these symptoms are more likely to affect people with preexisting conditions, such as asthma, chronic obstructive pulmonary disease (COPD), diabetes, chronic kidney disease, or heart disease, that doesn’t mean everyone else is in the clear, either.

Wildfire smoke may be just the thing that causes someone to develop allergies.

“I don’t know that we really have a good handle on [the mechanism of how wildfire smoke may enhance allergic sensitization],” said Jim Blando, PhD, chair of the Department of Epidemiology, Biostatistics, and Environmental Health at Old Dominion University, in an interview with HCPLive. “I don't think that's very well delineated. The thinking right now, without doing any kind of mechanistic studies on it, is that it simply can sensitize the immune system. That can end up resulting in [the] development of antibodies in your body that, then, when you're subsequently exposed to an allergen, you end up having a reaction to it.”

Blando compares this to poison ivy. Someone may not react the first time they brush against it, but once they've developed antibodies, later contact can trigger a reaction.

A Delayed Respiratory Effect of Wildfire Smoke

Blando and colleagues conducted a longitudinal study assessing the impact of wildfire smoke on respiratory peak flow performance in patients exposed to 2 separate wildfire events.4 Participants were drawn from a single clinic in a town of < 40,000 residents, located southeast of the fire area, roughly 25 miles from its center and approximately 10 miles from the southern border of the Great Dismal Swamp National Wildlife Refuge.

At the local clinic, allergic rhinitis and asthma were the most common respiratory diagnoses during both fire events. Allergic rhinitis affected 36% of patients during the first fire and 30% during the second, while asthma diagnoses varied by age group: 8% of adults and 15% of children during the first fire, and 10% of adults and 15% of children during the second.4

There was significant overlap between the 2 conditions. Roughly 80% of patients with allergic rhinitis during the first fire, and about 90% during the second, were also diagnosed with asthma. Because of this overlap, the study's subsequent analyses were limited to patients who had a diagnosis of allergic rhinitis, asthma, or both.

"We didn't see anything initially during the actual wildfire or immediately thereafter, so just kind of on a whim, being that they were allergy patients, and we figured there were probably a lot of allergens in the wildfire smoke, we thought, 'Why don't we just look and see?'” Blando said. “Lo and behold, when we did that, all of a sudden we found these statistically significant relationships, which was quite surprising to us.”

The study revealed peak flow performance declined significantly 1 year after the wildfires, with the decline most pronounced among women and Black patients, whose average measurements fell furthest below predicted levels.4 Investigators also identified a direct relationship between wind exposure and lung function: for every 1% increase in the amount of time wind blew from the fire toward the clinic's community, patients' peak flow dropped by an average of 2.21 L per minute a year later. The effect held even after accounting for age, BMI, sex, and race, suggesting wildfire smoke exposure, not just these underlying demographic factors, was driving the decline.

Wildfire Smoke Is Also Showing Up on the Skin

Blando's research points to the lungs and sinuses, but allergists are seeing wildfire smoke's effects show up on the skin, too.

Arianne Shadi Kourosh, a dermatologist at Massachusetts General Hospital, noticed a rise in eczema visits one summer, from under 20 patients to 160. That spike led her to review four years of summer records, where she found visit volume for these skin complaints tracked closely with air pollution severity. This pattern is consistent with other research linking wildfire pollution to increased eczema and psoriasis flares.

"Much of the atopic dermatitis... tends to be fairly immediate in terms of the exacerbations, generally the same week. [A] psoriasis… flare seems to be documented several weeks later, and that may be because that is more of a systemic inflammatory response as to more of a quick skin inflammatory response,” said Wynne Armand, MD, from Massachusetts General Hospital, in an interview with HCPLive.

Armand explained that patients with atopic conditions already have a weakened skin barrier, making it easier for particles to penetrate. In her clinic, she sees the same patients report worsening seasonal allergies, sinus symptoms, and watery eyes during smoke events.

“There's a lot of direct irritation to the eyes, the nose, the airway, and if somebody [already has] underlying conditions, and that includes allergic-type conditions like allergic rhinitis, hay fever, seasonal allergies, or asthma, that is often triggered by allergens, they can then also see worsening of their disease and have exacerbations," Armand said.

What Clinicians and Patients Can Do Now About Wildfire Smoke & Allergies

Armand's guidance for patients with allergic or skin conditions centers on limiting wildfire smoke exposure before it triggers symptoms. She recommends:

1. Monitor air quality
2. Wear a properly fitted N95 respirator
3. Use a mineral sunscreen containing zinc or titanium
4. Rinse exposed skin after time outdoors
5. Close windows and recirculate indoor air. Keep HVAC filters clean

“Make sure that you're in an environment with healthy, clean air,” Armand said.

The Wildfire Smoke & Allergy Research Is Still Catching Up

Both physicians agree the science connecting wildfire smoke to allergic disease is still developing. Armand pointed to a specific gap: distinguishing wildfire smoke's role in triggering flares in patients who already have allergic disease from its potential role in causing these conditions to develop in the first place.

“I personally feel pretty confident that as we look into it further, we are going to find a lot of evidence supporting that wildfire smoke is very allergenic," Blando said.

Watch our accompanying dynamic video on wildfire smoke’s impact on allergies here: Wildfire Smoke's Hidden Toll on Patients with Allergies

References

1. Miller B. Wildfire smoke is driving terrible air quality in major cities, but relief is coming. CNN. Published July 17, 2026. Accessed September 14, 2026. https://www.cnn.com/2026/07/17/weather/smoke-forecast-northeast-midwest

2. How Wildfire Smoke Affects Your Body. CDC. Published August 24, 2026. Accessed September 14, 2026. https://www.cdc.gov/wildfires/risk-factors/index.html

3. Vawter H. Three major US cities rank among worst air quality in the world as Canadian wildfire smoke invades America. Fox News. Published July 16, 2026. Accessed September 14, 2026. https://www.foxweather.com/extreme-weather/3-us-cities-rank-worst-air-quality-world-canadian-wildfire-smoke

4. Blando J, Allen M, Galadima H, Tolson T, Akpinar-Elci M, Szklo-Coxe M. Observations of Delayed Changes in Respiratory Function among Allergy Clinic Patients Exposed to Wildfire Smoke. Int J Environ Res Public Health. 2022 Jan 22;19(3):1241. doi: 10.3390/ijerph19031241. PMID: 35162264; PMCID: PMC8835059

5. Armand W. One surprising effect of wildfires: Itchy, irritated skin. Harvard Health Publishing. Published June 24, 2024. Accessed September 14, 2026. https://www.health.harvard.edu/blog/one-surprising-effect-of-wildfires-itchy-irritated-skin-202406243052