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Tess Eidem holds a jar of fungus used to produce allergens for research. A new study shows that UV light can reduce allergens in the air by double digits within a half-hour. Credit: Patrick Campbell/�鶹��Ѱ�����Boulder

Cats. Dust mites. Mold. Trees.

For people with allergies, even a brief whiff of the airborne allergens these organisms produce can lead to swollen eyes, itchy skin and impaired breathing.

Such allergens can persist indoors for months after the original source is gone, and repeated exposure can exacerbate, and even lead to, asthma.

What if you could just flip a switch and disable them? You can, according to new �鶹��Ѱ�����Boulder research.

“We have found that we can use a passive, generally safe ultraviolet light treatment to quickly inactivate airborne allergens,” said study author Tess Eidem, a senior research associate in the Department of Civil, Environmental and Architectural Engineering.

“We believe this could be another tool for helping people fight allergens in their home, schools or other places where allergens accumulate indoors.”

The findings were published in August in the journal

Why you can't kill an allergen

Walk into a room with a cat and, if you sneeze, it’s not actually the cat you are reacting to. It’s likely airborne flecks of a protein called Fel d1 produced in their saliva. The protein spreads when they lick themselves and ends up in microscopic flakes of dead skin floating in the air, a.k.a. dander. When we inhale these particles, our immune system produces antibodies that bind to the protein’s unique 3D structure, kicking off an allergic reaction.

Dogs, mice, dust mites, mold and plants all emit their own unique proteins, with their own unique structure. Unlike bacteria and viruses, these allergens can’t be killed because they were never alive.

“After those dust mites are long gone, the allergen is still there,” said Eidem. “That’s why, if you shake out a rug, you can have a reaction years later.”

Standard methods of reducing allergens—like vacuuming, washing walls, using an air filter and regularly bathing pets—can work OK but are hard to maintain, long-term studies show.

Eidem and co-authors Mark Hernandez, a professor of Civil, Environmental and Architectural Engineering, and Kristin Rugh, a microbiologist in the lab, sought a simpler way.

Tess Eidem pumps airborne allergens into a sealed chamber to test how UV light impacts them. Credit: Patrick Campbell/�鶹��Ѱ�����Boulder

Instead of eliminating the proteins that cause allergies, they sought to change their structure—much like unfolding an origami animal—so the immune system wouldn’t recognize them.

“If your immune system is used to a swan and you unfold the protein so it no longer looks like a swan, you won’t mount an allergic response,” explained Eidem.

UV light, their study suggests, can do that.

Let there be light

Previous research has shown that UV light can kill airborne microorganisms, including the virus that causes COVID-19.

It’s already used widely to disinfect equipment in hospitals, airports and elsewhere, but the bandwidth is typically so strong (a wavelength of 254 nanometers) that users must wear protective equipment to prevent damage to skin and eyes.��

Eidem used 222-nanometer-wavelength lights, a less-intense alternative considered safe for occupied spaces because it doesn’t penetrate deep into cells. (It does not come entirely without risks, including ozone production, she notes, so exposure should be limited.)

The team pumped microscopic aerosolized allergens from mites, pet dander, mold and pollen into an unoccupied and sealed 350-cubic-foot chamber. Then they switched on four lunchbox-sized UV222 lamps on the ceiling and floor.

When they sampled the air at 10-minute intervals and compared it to untreated, allergen-filled air via laboratory tests, they saw significant differences. In the treated samples, immunorecognition was reduced, meaning the antibodies no longer recognized many of the proteins and stuck to them.

UV 222 lights

After just 30 minutes, airborne allergen levels effectively decreased by about 20% to 25% on average, the study showed. Efficacy depended on the type of allergen, how long the light was on and what the allergen was floating in (dust, dander, liquid droplets, etc.) In one condition tested, after 40 minutes of UV light exposure, the cat allergen Fel d 1 had decreased by 61% compared to untreated air.

“Those are pretty rapid reductions when you compare them to months and months of cleaning, ripping up carpet, and bathing your cat,” said Eidem.

A portable allergy buster?

UV222 lights are already commercially available, mostly for industrial antimicrobial uses.

But Eidem envisions a day when companies could engineer portable versions for people to switch on when they visit a friend with a pet or clean out a dusty basement.

UV222 systems could also potentially protect workers frequently exposed to allergens, such as those who work around live animals or in cannabis grow houses where, , allergic reactions can be deadly.

One-in-three adults and children in the United States have allergies, according to the Centers for Disease Control. Eidem hopes her research, and more to come, can provide them with some relief—or even save lives.

“Asthma attacks kill about 10 people every day in the United States, and they are often triggered by airborne allergies,” she said. “Trying to develop new ways to prevent that exposure is really important.”