ACAAI 2011: Cutting Cat Dander and Allergic Response

BOSTON—Pets can cause a variety of health problems for those with sensitivities but there are environmental changes that can help, according to Dana Wallace, MD, PA, associate clinical professor, Nova Southeastern University, Davie, FL. Wallace spoke at the American College of Allergy, Asthma & Immunology’s annual meeting this morning.

Sixty-two percent of US households have a pet. Just two percent of the US population is allergic to cats but of allergic patients, 24 percent are allergic to cats and 17 percent are allergic to dogs.

Pet allergens, however, are in all homes, Wallace said. More than 90 percent of homes have measurable allergen to cats and dogs. Almost half (46 percent) of homes have at least one sample of Fel d1, the cast allergen. It takes just two micrograms to provoke allergic symptoms.

Wallace discussed a study conducted on schoolchildren with and without cats in their homes. Two classrooms used special school clothing, one classroom gave up having a pet at home and three control classes combined children with and without pets at home.

“There is a strong relationship between the number of cat owners among children in the class and measured cat allergen levels. Asthmatic children who are allergic to cats get nine times more asthma exacerbations when attending classes with many cat owners, especially after summer break.” Because it is lightweight, cat allergen is carried passively on clothing. This passive exposure to cat allergen may even contribute to allergic sensitization at school. School sandboxes have been found to have 8 micrograms of Fel d1, which Wallace said is high enough for both sensitization and symptoms.

Meanwhile, airborne cat allergens have been found to be coarse, fine or ultrafine. Sixty percent of airborne particles settle in two days but smaller particles take up to 14 days to settle. These airborne particles play an important role in the transmission of allergens outside the home, Wallace said.

The school study compared rates of Fel d1 among those who gave up their pet cat and those who wore special clothing at school to cut cat dander. Airborne cat allergen level in the intervention classes was four- to six-fold lower compared with the control classes. The level of cat allergens was three-fold higher on the clothing of cat owners than of children without cats in the control classes. Reflecting the ties people feel to their pets, rather than give up their cat, the group preferred to use the special school clothes.

More than 90 percent of cat allergic individuals are sensitized to Fel d1 and despite claims, even so-called hypoallergic cats secrete Fel d1. Fel d2, a minor cat allergen, is found in 22 percent of sensitized individuals. There is cross-reactivity with pork albumin. “The more we learn,” Wallace said, “the more questions we ask.”

Secondary prevention should be considered, she said, because many people have a positive skin test for cat allergens but no symptoms. And, it seems a multi-pronged approach is required for effective results. Multiple-allergen avoidance and multi-faceted environmental controls reduced asthma by 50 percent but single-allergen avoidance did not.