Childhood exposure to cats reduces asthma risk
provided by University of Virginia, HSC
hildren exposed to domestic cats have a decreased risk for developing asthma, according to a new study from the University of Virginia Health System. According to the Asthma and Allergy Foundation of America, asthma is the leading cause of chronic illness in children, and the incidence has increased more than 75 percent in school age children during the past 15 years. This study, published in the March 2001 issue of The Lancet, demonstrates that while children with high exposure to cat allergens develop an immune response to the animals, they do not exhibit symptoms of asthma.
The children's response to cat allergens also suggests that this form of tolerance could be a principal goal of immunotherapy, said Dr. Thomas Platts-Mills, professor of internal medicine and microbiology and lead investigator of the study. This data is also significant because it provides new information to explain the link between the environment and an increased risk for asthma.
Based on previous studies associating high exposure to cat allergen with decreased risk of sensitization, researchers at the University of Virginia investigated differing exposures to mite and cat allergens among 226 children (aged 12-14 years old), 47 of whom had symptoms of asthma and bronchial hyperreactivity. The children exposed to mites produced IgG and IgG4 antibodies, as well as increased sensitization (measured by IgE antibody concentration) to mite allergens. In contrast, many of the children with high exposure to cat allergens increased production of IgG and IgG4 antibodies, but did not become sensitized (or have increased IgE antibodies) to the cat allergens. The odds of sensitization of mite rather than cat in children with high exposures was 4.0. Sensitization of mite or cat allergens was the strongest independent factor for asthma (p<0.001).
Currently, there are more than 5.5 million children diagnosed with asthma. In the past 15 years, the number of childhood asthma related deaths has tripled in number. Several factors may contribute to an increased risk for the development of asthma. Environmental factors include dust mites cockroaches, mold and animal dander. Although there are several treatment options available, there is no definitive treatment or form of prevention.
The results of the study suggest that high exposure to cat allergens can induce a form of tolerance, which in turn makes it very unlikely that the increase in asthma has been caused by an increase in exposure.