Fluffy and Fido may look innocent, but they are at the heart of a controversy among allergy specialists on the influence pets have on a child's risk of developing allergies.
A growing body of evidence suggests that pets in the home may actually have a protective effect against developing pet allergies, at least for the first seven years of life, researchers at the recent annual conference of the American Academy of Allergy, Asthma and Immunology say.
Researchers at the Henry Ford Health System in Detroit and the Medical College of Georgia in Augusta followed more than 700 children living in two upper-middle-class communities north of Detroit from the time of their birth through age 6 or 7. More than half of the families had either a dog or a cat from the time the child was born.
At regular intervals the investigators analyzed the children's blood for substances called antibodies that trigger allergic reactions in the body. Antibodies are in turn triggered by allergens, substances in the environment that provoke allergic reactions. Symptoms of allergic reactions include difficulty breathing, facial swelling, and hives.
Researchers took skin-reaction tests that showed whether the children were sensitive, or allergic, to dog or cat allergens. They also collected data on the children's exposure to cigarette smoke and home and day-care environments, and they measured allergen levels in household dust and air samples.
By the age of 6 or 7, children who had lived with a dog or cat since the first year of life were significantly less likely to be allergic to dogs and cats. They even found that children who had a dog were less allergic to cats, and children who had a cat were less allergic to dogs. The association between a pet and decreased allergy risk was especially strong in first-born children.
"Our conclusion is that having a cat or dog in the house for some reason puts you at lower risk of having the indicators for allergy," says lead investigator Christine Cole Johnson, PhD, MPH. Johnson is director of Cancer Epidemiology Prevention and Control at the Josephine Ford Cancer Center in Detroit. Somehow, exposure to a dog or cat in early childhood protects a child against developing pet allergies.
Speaking at the American Academy of Allergy, Asthma and Immunology, Cole warned that this protection did not seem to extend to asthma: Approximately 10% of the children in their study developed that condition.
At the same conference, allergist Richard F. Lockey, MD, reported on a 41-year-old man with asthma who experienced two severe allergic reactions, one nearly fatal, while washing his pet ferret. He also developed hives on his abdomen when the animal touched his skin. Lockey and his colleagues at the University of South Florida and the VA Hospital in Tampa, Fla., found that extracts of ferret hair and urine elicited positive test responses from people known to have multiple allergies, including allergies to cats and dogs.
Lockey suggested that the current proliferation of pets could be contributing to the rapid growth in asthma and allergies seen in the past few years. He cited evidence that some people are even allergic to gerbils and guinea pigs, as well as dogs, cats -- and, apparently, ferrets. However, he concedes that most people resist recommendations to get rid of their pets and may not even think of their pets as animals.
"When you ask someone if they have an animal in the home, very often they'll say no, but if you ask if they have a dog or a cat, they say yes," he says.
But a growing number of clinicians now believe that blanket recommendations may be premature. "We must re-examine standards saying pets in the house are a risk factor for children," says Dennis Ownby, MD, professor of pediatrics and medicine at the Medical College of Georgia. Ownby, a co-investigator on the study of the protective effect of pets, tells WebMD, "Something about having a pet is associated with a lower risk of allergy. It is time to rethink our recommendations telling people to get rid of their pets." So Fluffy and Fido -- and perhaps their youngest masters -- can breathe easy for now.
- There has been a controversy among allergy specialists as to how pets influence childhood allergies, but new evidence shows that pet ownership in early childhood may have a protective effect against developing pet allergies.
- In a study of more than 700 children, those who lived with a cat or a dog since the first year of their life were less likely to show indicators for allergy, and this effect was even more pronounced in first-born children.
- Researchers caution that this protective effect may not extend to asthma, and owning a pet may cause severe asthma attacks in some people.