Early exposure to pets and risks of childhood allergies
June 13, 2011 — Exposure to pets in early life may not raise the risk for childhood allergies and may even be protective, according to the results of a birth cohort study reported online June 13 in Clinical & Experimental Allergy.
"Prior research about whether keeping a dog or cat at home causes allergies to that pet has been limited to outcomes in early childhood," write Ganesa Wegienka, MS, PhD, from the Department of Public Health Sciences at Henry Ford Hospital in Detroit, Michigan, and colleagues. "...In this report, we used a life course approach, similar to our examination of overall sensitization, to further investigate the relationships between exposure to indoor dogs and the risk of dog sensitization and exposure to indoor cats and cat sensitization."
The goal of the study was to examine the association between lifetime dog and cat exposure and allergic sensitization to the specific animal at age 18 years among 566 participants enrolled in the Detroit Childhood Allergy Study birth cohort during 1987 to 1989.
Lifetime indoor dog and cat exposure, defined as the pets spending at least 50% of their time inside the house, was determined from annual interview data from childhood and follow-up interviews at age 18 years. Sensitization to dog or cat was defined as animal-specific immunoglobulin E (IgE) levels of 0.35 kU/L or more. Exposure was analyzed separately for dogs and cats and for first year, by age groups, and cumulative lifetime exposure.
Compared with boys who did not have an indoor dog in the first year of life, those who did had half the risk of being sensitized to dogs at age 18 years (relative risk [RR], 0.50; 95% confidence interval [CI], 0.27 - 0.92). This association was not observed in girls. For boys and girls delivered by cesarean, the RR was 0.33 (95% CI, 0.07 - 0.97).
Teens who had an indoor cat in the first year of life had a reduced risk (RR, 0.52; 95% CI, 0.31 - 0.90) of being sensitized to cats. Neither cumulative exposure nor exposure at any other age was associated with the risk for sensitization.
"This research provides further evidence that experiences in the first year of life are associated with health status later in life, and that early life pet exposure does not put most children at risk of being sensitized to these animals later in life," Dr. Wegienka said in a news release.
Limitations of this study include incomplete follow-up data on all participants enrolled in the original study, use of parental allergic history that was based on maternal report, and lack of lifetime measurements of the participants' actual exposures to dog or cat allergen. In addition, although the investigators controlled for a parental history of allergy, this history of allergy is not necessarily specific for dog or cat allergy.
"Dog and cat exposure has been reported to be associated with recurrent asthma exacerbation in sensitized individuals," the study authors conclude. "By preventing sensitization, hopefully exacerbations would be reduced or eliminated. ...An insightful and logical next step would be to further delineate the effects of pets on immune development during smaller time windows (e.g. the first month, the first 3 months) in the first year of life."
The Fund for Henry Ford Hospital and the National Institute of Allergy and Infectious Diseases supported this study. The study authors have disclosed no relevant financial relationships.
Clin Exper Allergy. Published online June 13, 2011.
"Prior research about whether keeping a dog or cat at home causes allergies to that pet has been limited to outcomes in early childhood," write Ganesa Wegienka, MS, PhD, from the Department of Public Health Sciences at Henry Ford Hospital in Detroit, Michigan, and colleagues. "...In this report, we used a life course approach, similar to our examination of overall sensitization, to further investigate the relationships between exposure to indoor dogs and the risk of dog sensitization and exposure to indoor cats and cat sensitization."
The goal of the study was to examine the association between lifetime dog and cat exposure and allergic sensitization to the specific animal at age 18 years among 566 participants enrolled in the Detroit Childhood Allergy Study birth cohort during 1987 to 1989.
Lifetime indoor dog and cat exposure, defined as the pets spending at least 50% of their time inside the house, was determined from annual interview data from childhood and follow-up interviews at age 18 years. Sensitization to dog or cat was defined as animal-specific immunoglobulin E (IgE) levels of 0.35 kU/L or more. Exposure was analyzed separately for dogs and cats and for first year, by age groups, and cumulative lifetime exposure.
Compared with boys who did not have an indoor dog in the first year of life, those who did had half the risk of being sensitized to dogs at age 18 years (relative risk [RR], 0.50; 95% confidence interval [CI], 0.27 - 0.92). This association was not observed in girls. For boys and girls delivered by cesarean, the RR was 0.33 (95% CI, 0.07 - 0.97).
Teens who had an indoor cat in the first year of life had a reduced risk (RR, 0.52; 95% CI, 0.31 - 0.90) of being sensitized to cats. Neither cumulative exposure nor exposure at any other age was associated with the risk for sensitization.
"This research provides further evidence that experiences in the first year of life are associated with health status later in life, and that early life pet exposure does not put most children at risk of being sensitized to these animals later in life," Dr. Wegienka said in a news release.
Limitations of this study include incomplete follow-up data on all participants enrolled in the original study, use of parental allergic history that was based on maternal report, and lack of lifetime measurements of the participants' actual exposures to dog or cat allergen. In addition, although the investigators controlled for a parental history of allergy, this history of allergy is not necessarily specific for dog or cat allergy.
"Dog and cat exposure has been reported to be associated with recurrent asthma exacerbation in sensitized individuals," the study authors conclude. "By preventing sensitization, hopefully exacerbations would be reduced or eliminated. ...An insightful and logical next step would be to further delineate the effects of pets on immune development during smaller time windows (e.g. the first month, the first 3 months) in the first year of life."
The Fund for Henry Ford Hospital and the National Institute of Allergy and Infectious Diseases supported this study. The study authors have disclosed no relevant financial relationships.
Clin Exper Allergy. Published online June 13, 2011.
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