Plenty of people develop allergies to animals, with symptoms ranging from runny noses to life threatening asthma. Mostly, we hear about allergies to cats and dogs. But up to a quarter of people who work with lab animals, chiefly rodents, also develop an allergy to the critters’ dander or some other allergen. A Korean study now reports that office workers and others who work at a facility where animals are housed can become allergic — even if they never touch the animals.
Perhaps it’s something in the air, the scientists speculate.
Whatever it is, they conclude in the May Annals of Allergy, Asthma and Immunology, such indirect exposures appear to “be as risky for sensitization to lab-animal allergens as direct exposure [to animals].”
Physicians with the Seoul National University College of Medicine and other biomedical organizations recruited 107 people who worked at the Korean Centers for Disease Control and Prevention to undergo skin-prick tests for allergies and to take questionnaires about allergic symptoms. Of these participants, 33 were office workers at the agency who had no direct contact with lab animals. Another 30 people signed on as control volunteers; they worked some place else and had no contact with lab animals or family members who worked with animals.
The researchers assessed allergy symptoms that started in any of the volunteers after they had begun working at their current jobs. These included all of the common environmental allergies, such as to pollen, latex, cockroaches, fungi, pets and farm livestock. Tests also probed for specific sensitivity to allergens from lab animals: mice, rats, guinea pigs, hamsters and rabbits.
Roughly one-quarter of the animal workers at Korea’s CDC had workplace-related allergies, although less than half that many exhibited sensitivity to lab animals. “These results indicate that there is a weak correlation between sensitization to lab-animal allergens and clinical symptoms,” they say. One hypothesis they offer: Many of these people may have been breathing “airborne endotoxin.”
A poisonous structural constituent of certain bacteria, endotoxin can be shed into the air when these germs die and fall apart. Common symptoms of endotoxin inhalation include airflow obstruction, coughing, nasal stuffiness and hyper-reactivity of the lungs' bronchial airways. Lab animal workers at Korea’s CDC were more likely to have exposure to endotoxin, the new study finds.
So this airborne bacterial toxin may provoke allergies in lab-animal workers who show no sensitivity to lab animals, the authors of the new study note. So might exposures to storage mites and other materials, they point out.
But the big surprise was that allergies to mouse and rat urine were absent in the control group but present in the 3 to 6 percent among Korean CDC workers — and it made no difference if they worked with animals or only in offices at the facility.
The take-home message, the study’s authors argue, is that if allergens escaping from animal labs are contributing to even the office worker’s sensitivity, then everybody at a facility that uses animals “needs to be carefully protected from laboratory allergen.” Indeed, the researchers point out, because many people with preexisting allergies may seek office work to avoid exposure to common animal allergens, this segment of the workforce may actually be more susceptible to mouse- or rat-associated allergens than are people who willingly choose to work with the critters.
Jang, J.H., et al. 2009. Allergic Rhinitis in Laboratory Animal Workers and Its Risk Factors. Annals of Allergy, Asthma & Immunology 102(May):373.