my personal edition > allergy other > news


  E-Mail this DGDispatch to a colleague

DGDispatch

Children 2 to 4 Years Old Can Lose Antigen-specific IgE to Aeroallergens: Presented at AAAAI

By Paula Moyer

SAN FRANCISCO, CA -- March 24, 2004 -- Young children who are initially sensitised to an aeroallergen can lose that sensitivity in a 2-year time period, and are more likely to do so if the family acquires a dog, according to findings presented here March 21^st at the American Academy of Allergy, Asthma, and Immunology's 60^th Annual Meeting.

This finding is contrary to the common assumption that young children's aeroallergen sensitisation is persistent, said principal investigator Michael R. Simon, MD.

"We have thought that, if a 2-year-old child had developed an allergy to an air-borne substance, that the child would continue to be allergic," said Dr. Simon, Professor of Paediatrics and Internal Medicine, Wayne State University, Detroit, Michigan, United States. "We wanted to test the validity of this assumption after 2 European studies had shown that school-age children can lose their allergies, and that exposure to farm animals increases the likelihood of this happening."

He and his co-investigators obtained data on children who were enrolled in the Childhood Allergy Study in suburban southeast Michigan. The children were tested for the presence of immunoglobulin E (IgE) that was specific to Dermatophagoides farinae, D. pteronyssinus, dog, cat, short ragweed, and timothy grass. The investigators defined a child as sensitised if there were measurable aeroallergen-specific circulating IgE to any of these 6 aeroallergens in a blood sample.

Among the 339 children who were tested at ages 2 and 4 years, 48.7% initially had at least 1 positive allergen-specific IgE test. At age 4 years, 37% who had had a positive test became negative to all tests upon retesting. Among these children, 104 were positive at both testing times, and 109 were negative on both occasions. Among the 174 children who were initially negative, 37% became positive at the second testing period.

Among the 165 children who were initially sensitised, the families of 25 acquired a dog; 139 had no dogs, and the pet status of 1 child was unknown. Among the 139 with no dog, 14.4% lost their sensitivity to all tested allergens. Among the 25 with a dog, 40.0% lost their sensitivities. Removing an animal from the home had no effect on sensitivities, Dr. Simon said.

These findings should not suggest that a child who is allergic to dogs and has allergy symptoms in the presence of a dog should acquire one, he stressed.

"An individual who has a symptomatic allergy to dogs and is exposed to a dog will have increased symptoms," he said. "For people with allergy symptoms, the source of the allergen should still be removed from the house."

He added that the reason for dogs' protective effect is unknown, but thought to be related to the introduction of canine endotoxins to the immune system.

"Our results have significant implications for assessing allergy in young children over time, as well as for the study of the immunological effects of allergen-injection immunotherapy," he said.


[Study Title: Loss Of Antigen-Specific IgE to Aeroallergens in Children Between Ages Two and Four Years. Abstract 463]

E-Mail this DGDispatch to a colleague

To print, use this version