Canadian wildfire smoke pushed air quality into "hazardous" territory across multiple US states this summer.¹ Pulmonary and cardiovascular effects of wildfire smoke exposure are well documented, yet allergy-specific consequences have drawn comparatively less research attention. Clinicians treating allergic rhinitis and asthma in wildfire-prone regions currently have little data on how long these effects persist after smoke exposure ends or whether repeated exposure compounds the risk.

Jim Blando, PhD, chair of the Department of Epidemiology, Biostatistics, and Environmental Health at Old Dominion University, studied allergy clinic patients exposed to 2 wildfire events near North Carolina's Dismal Swamp.² Allergic rhinitis affected 36% of patients during the first fire and 30% during the second, with roughly 80% to 90% of these patients also diagnosed with asthma.² Peak flow performance declined significantly 1 year after exposure, with the steepest drops among women and Black patients.²

For every 1% increase in wind time blowing from the fire toward the clinic's community, peak flow fell by an average of 2.21 L per minute a year later.² The finding raises questions about whether delayed immune sensitization plays a role in allergic reactions following other environmental exposures beyond wildfire smoke.

In the following interview with HCPLive, Blando discusses the delayed respiratory effect his team identified, a possible immunologic mechanism behind the reaction, and where research on wildfire smoke and allergic disease still falls short.

Q&A: Wildfire Smoke and Delayed Allergic Sensitization, with Jim Blando, PhD

HCPLive: What prompted you to look at the respiratory function a full year after wildfire events, rather than during or immediately after the smoke exposure?

Blando: We did look at it immediately after the exposure period, but we didn't see strong… [or] statistically significant results. Originally, we intended to look at respiratory peak flow performance among allergy clinic patients during the wildfire [itself] because logically that's when they would experience a decrease in their lung function.

We were just about to put the study away. On a whim, I thought to myself, “Well, these are allergy patients. Sometimes with allergies, you can have a delayed reaction.” Wildfire smoke probably has a lot of allergens, since it's basically burning forests, or in this case, a burning peat swamp… in the Dismal Swamp in North Carolina.

Lo and behold, when we [looked further down the road], we found these statistically significant relationships, which was quite surprising to us.

[In the] literature, we only found 1 other study that looked at a delayed response more than 2 weeks out from the wildfire, so [this was a] pretty novel finding. Sometimes it's important [in] research to explore all different avenues, even for things that you don't necessarily expect. This was one of those cases where we didn't really think we're going to find something, but then, in fact, we did.

HCPLive: Given what you found in North Carolina, do you expect similar delayed effects in other regions with more frequent or severe wildfire seasons?

Blando: I [would] assume this would apply to other regions as well. The 1 other study that was published a little bit before [ours], [which] looked a few months out, was in Montana.

There haven't been very many studies looking at this. There are a few studies [on] delayed response [in] wildland firefighters in Greece, but [otherwise] there isn’t much in the literature.

HCPLive: Can you walk through the mechanism of how wildfire smoke may enhance allergic sensitization?

Blando: I don't think that's very well delineated. The thinking right now, without doing any kind of mechanistic studies, is that it simply can sensitize the immune system…resulting in [the] development [of] antibodies in your body. Then, when you're subsequently exposed to an allergen, you end up having a reaction to it.

Some people [think it could be] an IgG-mediated reaction, which is a longer-term allergic reaction, but I don't think it's been very well delineated, and it probably [varies]…depending on the specific allergen. It's like when somebody has poison ivy; the first time you're exposed, you don't necessarily get a reaction, but once you have those antibodies, you're going to react…on subsequent exposures.

HCPLive: Did you see differences in how wildfire smoke affects different types of allergies, such as seasonal allergic rhinitis, food allergies, or skin conditions?

Blando: In this particular study, we did not differentiate that. Almost all of [the patients] had allergic rhinitis. They either had allergic rhinitis and/or allergic asthma, as diagnosed by an allergist. It stands to reason if you're breathing in large particles and they're settling in your nose or nasal passages, and you have allergic rhinitis, that that would precipitate an allergic reaction.

HCPLive: For patients managing seasonal allergies who also live through reoccurring wildfire seasons, is there any evidence that their baseline allergy severity is trending worse year after year because of the cumulative smoke exposure?

Blando: I haven't seen any studies in the literature that have looked at the cumulative smoke exposure and [its] impact. Right now, where we're at is possibly the recognition that wildfire smoke can act as an allergen. I don't think anybody's taken it any steps further than that.

We actually had a really difficult time getting our paper published because a lot of peer reviewers couldn't understand how this could possibly be. They seemed to think that the effect has to be fairly immediate. I'm not even sure if the entire research community really widely accepts [it yet], [but] from an immunologic perspective, it completely makes sense.

We have plenty of examples of this in the occupational health literature. Workers [exposed to] glutaraldehyde or isocyanates [are] well known…to develop allergic reactions and asthma as they work with these chemicals for longer periods of time because of the cumulative exposure.

One could argue that it makes sense that the cumulative baseline could change. That seems like a logical conclusion. I don't think at this time there are any studies that have definitively shown that for wildfire smoke, but it wouldn't surprise me if that was the case.

HCPLive: If a patient with no prior allergy history moves or lives in a wildflower-prone region, what would you tell them about their risk of developing allergies down the line?

Blando: What we would always tell people is to consult and work with your healthcare provider, especially if [they] notice that you are developing allergies.

Wildfire smoke [is] like anything else. If your family [gets] a dog, it’s possible that you could get sensitized to the allergens in the dog hair. If you're in an area that's susceptible to wildfires, you could develop allergies, or if you already have preexisting allergies, they could [worsen]. That's where you would work with your healthcare provider to treat the symptoms and take care of your allergies.

HCPLive: Are there certain groups, such as children, older adults, or people with a family history of allergies, more likely to see their allergies worsen from the wildfire exposure?

Blando: [We often find that the] very young, the very old, and people with preexisting respiratory or heart conditions may be more susceptible to the adverse effects of air pollutants, including wildfire smoke. If you have preexisting allergies, I would imagine that you'd be more susceptible to a more severe reaction to it.

HCPLive: Much of the wildfire health research focuses on asthma and pulmonary outcomes. Why do you think allergy-specific consequences have gotten less attention?

Blando: A lot of the air pollution and health studies, especially [around] smoke and particles…tended to be descriptive and looked at very broad categories of adverse health outcomes: pulmonary effects, cardiac effects, and overall mortality. [From] a logical reasoning perspective, one would certainly look at respiratory conditions [first] because it's air you breathe, so your pulmonary system is directly involved. But when you talk to immunologists, you find that the immune system underlines a lot of aspects of health, and hopefully our study will move people to look further into [this area].

HCPLive: As wildfires become more frequent and severe across the country, do you expect allergy prevalence to rise as a result?

Blando: We are seeing allergy prevalence rise in epidemiologic studies. Climate change is increasing the length of the growing [and] allergy season[s]. Plants are blooming earlier; they're producing more pollen. These are contributing to [the] increase in allergies.

Wildfires are one part of that. Wildfires are getting bigger; they're happening more frequently. They're burning longer. They're starting earlier. The same is true for normal plant growth and pollination.

There were some studies that showed that the increase in nighttime temperatures may [cause] the pollen [from] some trees to [become] more allergenic. All of these factors together [are] likely why we're seeing an increased prevalence of allergies.

HCPLive: How confident are you in the current body of research connecting wildfire smoke to allergic disease versus how much is still assumption-based on general air pollution research?

Blando: Right now, a lot of [it is] assumption. Even I'm doing research in this specific area, and I'm still assuming because we don't yet have the studies other than our [2022] study and another study published shortly before then.

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, [but] that's one thing about research. You never know what you're going to find out.

For more on this topic:

1. Wildfire Smoke's Hidden Toll on Patients with Allergies (video)
2. How Wildfire Smoke Triggers Allergic Disease Long After It Clears (feature)

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. 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;19(3):1241. doi:10.3390/ijerph19031241