Stories Archive - New England Society for Biomedical Research

Allergens in the Spotlight

Have you ever wondered what happens after you flush the toilet? Where does all that water and sewage go? In most parts of the world with sanitation systems to manage sewage, everything you flush down the toilet ends up at a sewage treatment facility. These facilities collect and treat the sewage to make sure the waste water is safe before it gets released back into the environment. Sewage treatment is a critical public health intervention that has saved more lives than any other public health measures except for vaccines.

The people responsible for making sure that your drinking water is safe and not contaminated by sewage are civil and environmental engineers. Dr. Mark Hernandez is Professor of Civil, Environmental, and Architectural Engineering at the University of Colorado in Boulder, CO.

While in graduate school, Dr. Hernandez studied how microorganisms interact with each other and the environment during the process of sewage treatment. The staff at the treatment plants used to come to him with questions about the air they were breathing. “We know we’re treating the water to make it safe,” they would say, “but what about the air quality in our treatment plants?” Dr. Hernandez responded: “Great question, let’s find out.”

Since that time, Dr. Hernandez has spent his career trying to answer this and other questions about the biological aspects of indoor air pollution. He has developed new methods for characterizing the indoor air quality and implemented a variety of interventions to improve indoor air quality, especially in schools and elder care facilities. “I care most about the places that people don’t have a choice to be in—children have to be in school, and elders who require care need the support of skilled care facilities. We need the air in those places to be as clean as possible.”

Every Breath You Take

As long as humans have been living indoors, there have been problems with infections and allergies¹. Every generation of humans living inside have faced pandemics² of infectious diseases, most recently the COVID-19 pandemic. The COVID-19 pandemic put a spotlight on many indoor spaces with poor air quality, including many schools. Indeed, classic airborne diseases are again on the rise as we witness the unwelcome return of measles³, whooping cough⁴, and tuberculosis⁵, among others.

One well-known way to improve indoor air quality is using high efficiency air filters that catch tiny particles in the air, especially ones that can cause infection and trigger asthma⁶.

Figure 1.

High efficiency air filters catch tiny particles in the air.

[Source: https://commons.wikimedia.org/wiki/File:HEPA_Filter.png]

In the wake of the COVID-19 pandemic, Dr. Hernandez partnered with the Denver Public Schools, the largest public school district in the Mountain West region of the US, to improve air quality in elementary schools by installing quiet air filters directly inside classrooms. This work showed that simple air filtration systems could dramatically improve the quality of air in school classrooms as well as help the existing ventilation systems do a better job. Dr. Hernandez has since expanded this work to include schools across the state of Colorado. He has partnered with researchers at the Colorado School of Public Health based at Anschutz School of Medicine to measure the impacts of this improved air quality on school absences due to respiratory illnesses.

Allergens in the Air

Recently, Dr. Hernandez has turned his attention to another common airborne issue: allergens. An allergen is any substance that can provoke an allergic reaction⁷ when you come in contact with it, including inhaling it. Not everyone is allergic to the same allergens or has the same kind of allergic reaction.

In people who are sensitive to a specific allergen, the immune system⁸ can rapidly produce a family of specialized proteins called immunoglobulin E⁹ (IgE) that recognize and bind to one or more allergens. The binding of IgE and the allergen in people sensitive to the allergen can hyperactivate the immune system in ways that lead to allergic reactions. It is important to note that much of our understanding of the pathways involved in allergies, allergic reactions, and asthma is based on research first conducted in cells and animal models.

Allergens found in the air are known as airborne allergens, or aeroallergens¹⁰ for short. The most common aeroallergens are proteins that can be generated both indoors and outdoors, including by insects like dust mites¹¹ and cockroaches, mammals like dogs and cats, and plants. While some allergic reactions can be mild, such as sneezing and coughing, others can cause severe symptoms and potentially become life-threatening. Scientists have found ongoing exposure to certain aeroallergens can be associated with the development of asthma, as well as trigger asthma attacks¹².

As described in previous stories, asthma is a chronic respiratory disease that leads to inflammation¹³ and narrowing of the airways. While asthma cannot be cured, it can be managed through medication and lifestyle interventions, including avoiding potentially triggering¹⁴ allergens. Unfortunately, avoiding allergens is not always possible, especially in places like schools where students don’t have control over their indoor environment.

Dr. Hernandez spends much of his time thinking about ways engineering can be used to improve indoor air and the quality of life for people who spend time indoors, particularly school children and the elderly. While air filters can reduce the levels of airborne allergens to a certain extent, further reductions could lead to better air quality. Another approach is to alter the proteins that cause allergies in such a way that the immune system no longer recognizes them. Dr. Hernandez hypothesized one way to alter aeroallergens might be the use of a new generation of ultraviolet (UV) light¹⁵ that is safe for human skin and eyes.

Lighting Up Allergens

UV light is one of many ways that energy moves as waves along the electromagnetic spectrum¹⁶. The most well-known part of the electromagnetic spectrum is visible light¹⁷, which comes in different wavelengths¹⁸ that we experience as colors. UV light has shorter wavelengths and carries more energy than visible light.

Figure 2.

Electromagnetic spectrum including visible light and ultraviolet light.

[Source: https://www.nist.gov/sites/default/files/images/2024/09/11/EMSpec-final.png]

Like visible light, UV light also has different wavelengths, and the properties of the UV light vary based on wavelength. Certain wavelengths of UV light, namely UV₂₅₄, can damage DNA, while others, such as UV₂₂₂, can alter proteins without causing genetic damage. UV₂₅₄ is currently used in some hospital and laboratory settings to disinfect surfaces and equipment because it attacks the genetic material of organisms like viruses and bacteria. This type of UV light must be used carefully, as it is the same wavelength that causes skin damage. For this reason, UV₂₅₄ is typically used in unoccupied spaces or with protective equipment to limit human exposure.

On the other hand, UV₂₂₂ is available in a new generation of consumer lamps that can provide “occupant-safe” UV light because the light waves alter proteins but do not lead to DNA damage. The effects of different wavelengths of UV lights have been demonstrated in animal and human cells and animal models, as these experiments cannot be conducted in humans.

Dr. Hernandez sought to take advantage of the effects of UV₂₂₂ on proteins to see if allergens could be altered to limit their reactivity with the immune systems of sensitive people. As part of his work improving indoor air quality, Dr. Hernandez had previously built an airtight chamber, about the size of a bathroom in your home, to model different air quality interventions. Dr. Hernandez and his team keep the chamber at a consistent temperature and humidity throughout testing, as these factors can also influence air quality interventions.

Figure 3.

Ten-by-ten-foot cubic chamber in Dr. Hernandez’s laboratory. Four fans are placed in the bottom four corners of the chamber facing up, and four UV lights are placed in two upper corners and two lower corners of the chamber. An air filter is located inside the chamber (labeled HEPA), and measurements are taken using tools outside the chamber.

[Source: Eidem et al 2025, Figure 1]

During each trial, a single allergen was released into the chamber and mixed with the chamber air by fans. Between each trial, Dr. Hernandez’s research team used high quality air filtration to remove the allergens from the chamber air and avoid any contamination.

Figure 4.

Dr. Marina Nieto Caballero, a member of Dr. Hernandez’s lab, operates the 10 cubic meter chamber from the outside.

[Source: https://www.colorado.edu/faculty/hernandez/lab-services]

At the beginning of the trial, the aeroallergens were introduced to the chamber via nebulization¹⁹, the process of converting a liquid into a spray. The researchers used a specific type of nebulizer called a Collison nebulizer that converts the liquid allergen into a fine spray. The nebulized aeroallergen was mixed with the chamber air for an initial 10 minutes at the start of each trial.

Figure 5.

Collison nebulizer used to convert liquid allergen into a fine spray that mixed with chamber air.

[Source: https://chtechusa.com/products_tag_lg_collison-nebulizer.php]

The researchers collected air samples using two methods: BioSpot condensation²⁰ collection and Micro-Orifice Uniform Deposit Impactor (MOUDI) collection. Biospot takes particles from the air and gently concentrates it into a liquid, which can then be analyzed. BioSpot samples were taken at baseline and every 10 minutes thereafter, for a total of 7 samples per allergen per 60-minute trial.

Figure 6.

BioSpot collector used to take air samples and quantity the amount of aeroallergen in the air at a given time period.

[Source: https://aerosoldevices.com/wp-content/uploads/2023/03/BioSpot-VIVAS-310-angle-1.png]

While BioSpot is a great method for evaluating the total contents of the chamber air, it can’t differentiate between different particle sizes. For this reason, the researchers also collected a sample using MOUDI, which allowed the researchers to understand the relative sizes of the different particles in the air. Based on particle size, the researchers could determine which parts of the lungs might be affected.

Figure 7.

Micro-Orifice Uniform Deposit Impactor (MOUDI) used to separate particles in the chamber air sample, including aeroallergens, by size.

[Source: https://www.standard-groups.com/en/FilterMaterial/1018.html]

The researchers tested both purified and dust-borne aeroallergens. It was important to compare the purified and dust-borne forms of aeroallergens because dust could potentially interact with the allergen in certain ways. For example, elements in the dust might stabilize the allergens or promote decay, thus influencing the effects of UV light.

Figure 8.

Timeline of each trial of the experiment. Allergens were mixed with chamber air through aeroallergen Collison nebulization for the first 10 minutes. Biospot collection occurred every 10 minutes, and MOUDI collection occurred between 6 and 26 minutes.

[Source: Eidem et al 2025, Figure 2]

The experiment included five purified allergens: Fel d 1 (cats), Can f 1 (dogs), Bet v 1 (birch pollen), and Der p 1 and Der f 1 (dust mites). These allergens were also tested in dust-borne form, with the addition of Asp f 1 (black mold) and Phl p 5 (timothy grass pollen).

Figure 9.

Allergens tested in this study include proteins derived from birch pollen (top left), dust mites (bottom left), timothy grass (middle), cats and dogs (upper right) and black mold (bottom left).

[Source: https://commons.wikimedia.org/wiki/File:The_catkins_are_out_-_detail_-_geograph.org.uk_-_1191141.jpg; https://commons.wikimedia.org/wiki/File:House_Dust_Mite.jpg; https://commons.wikimedia.org/wiki/File:Timothy_grass.jpg; https://commons.wikimedia.org/wiki/File:Black_mold_in_a_building.JPG]

As the researchers expected the quantity of aeroallergen in the chamber air to naturally decrease over time, they first ran the experiment on all the allergens without UV exposure to establish a baseline. Next, the researchers repeated the experiments with UV₂₂₂ treatment.

After completing all the trials, the researchers analyzed the air samples using a technique called immunoassay testing²¹. Immunoassay testing measures the presence of a specific molecule by using a complementary protein. In this case, the researchers used immunoassay testing with mammal antibodies²² that recognize the specific allergen. This testing mimics the interaction between IgE and allergens that happen in the human immune system of people who are sensitive to the allergen. The researchers converted the results of the immunoassay into a percentage of the allergen remaining in the chamber air and compared the results with and without UV₂₂₂ exposure.

Figure 10.

UV₂₂₂treatment significantly reduces dust-borne aeroallergens in the chamber compared to baseline.

[Source: Eidem et al 2025, Figure 5]

Figure 11.

UV₂₂₂treatment significantly reduces purified aeroallergens in the chamber compared to baseline.

[Source: Eidem et al 2025, Figure 6]

Overall, the UV₂₂₂ intervention decreased the amount of dust-borne allergen in the chamber air by 25% and the amount of purified allergen in the chamber air by 20% in less than an hour. There was some variability noted between allergens. For example, Fel d 1 (cats) was the least affected by UV₂₂₂ light exposure and Bet v 1 (birch pollen) was the most affected.

More research is needed to understand how specific doses of UV₂₂₂ light and different components of dust might impact the susceptibility of an allergen to UV₂₂₂ light intervention. In addition, these researchers hypothesize the reductions in aeroallergens seen in these experiments might lead to reduced symptoms in people sensitive to those allergens, but more research is needed to determine whether this is the case.

“We’re very encouraged by these results,” commented Dr. Hernandez. “They show proof of concept that UV₂₂₂might make a difference in the amount of airborne allergen found in indoor air.” Dr. Hernandez and colleagues acknowledge that any single intervention to reduce allergen exposure is unlikely to work effectively on its own. However, multiple strategies working together might provide significant relief. The researchers envision the possibility that UV₂₂₂ light might be used as part of a multi-pronged approach to improve indoor air quality and reduce aeroallergens.

The next step is to test UV₂₂₂lamps in real life settings. Dr. Hernandez is hopeful that some of the schools that have successfully used air filtration interventions to improve indoor air quality will also be interested in testing the effects of UV₂₂₂lamps on aeroallergen exposure under carefully controlled conditions.

In ongoing and future work, Dr. Hernandez continues to test a variety of interventions to improve indoor air quality in classrooms. “We’ve sent people to the moon,” concluded Dr. Hernandez, “but we still continue to struggle with indoor air quality. Let’s give our air the attention it deserves, especially in places like schools where children don’t have a choice.”

Dr. Mark Hernandez is a professionally registered civil engineer and Professor of Civil, Environmental, and Architectural Engineering and Professor of Biomedical Engineering at the University of Colorado Boulder, where he has been on the faculty for 30 years. His research focuses on the microbiology of air pollution and develops interventions to improve indoor and outdoor air quality. When not in the laboratory, Dr. Hernandez enjoys walking in the mountains and classic ballroom dancing.

Every Breath You Take

Allergens in the Air

Lighting Up Allergens

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