A recent study published in The Lancet shows that high levels of cat allergen in the home may decrease the risk of children developing asthma. This is at variance to house dust mite allergens, for example. In this case, higher levels of exposure increase the likelihood of a person to produce IgE antibodies, of becoming allergic and developing asthma.

Levels of antibodies to cat allergen were measured in children who were also tested for asthma. The concentration of cat allergens in the children's homes were also recorded. Surprisingly, low-to-moderate amounts of cat allergen seemed to trigger allergy, whereas high amounts reduced both IgE antibodies and the likelihood of asthma; the children's immune systems were prompted to predominantly make antibodies of the IgG and IgG4 classes rather than IgE. However, high exposure is not protective for all children, it can be a risk factor for others. If the child shows symptoms and has a positive skin test to cat allergen, then removal of the cat from the household is recommended.

T. Platts-Mills, et al. (2001) Sensitisation, asthma, and a modified Th2 response in children exposed to cat allergen: a populations-based cross-sectional study. The Lancet 357, 752-56.

Reported by the (National Institute of Allergy and Infectious Diseases) NIAID Office of Communications and Public Liaison.
8 March 2001