Dog Ownership and Incidence of Eczema in Children

This study examined the factors that affected the risk of allergies and related skin conditions such as eczema in 4-year old children. The examined children belonged to parents who had allergies, which had made the children prone to similar allergies. Results showed that not owning a dog raised the risk of eczema in children prone to dog allergies by four times. Owning a canine pet, however, negated the risk of eczema even in allergy-prone children. The results were exactly the opposite with cats.

Over the last 30 years there has been an increase in allergies manifesting as skin lesions called eczema. Eczema affects 15 to 30 percent of children and 2 to 10 percent of adults all over the world. Eczema and allergies are said to be the predecessors of asthma in many children. Genes inherited from allergy-prone parents, as well as environmental triggers play their respective roles in causing allergies. Earlier studies have shown that owning a canine pet may reduce the risk of eczema in kids. However, there have been contradictory results regarding ownership of cats. While some researchers found that owning a cat reduced the risk of eczema, other researchers’ concluded differently. This study attempted to resolve this differentiation.

* Around 635 children belonging to a study group called “The Cincinnati Childhood Allergy & Air Pollution Study (CCAAPS)” were included in the study. These children had parents who suffered from allergic tendencies, which significantly raised their risk of being allergic.
* From the age of 1 year to 4 years the infants who were a part of the study were tested once a year for various types of allergies caused by dogs, cats, milk and eggs.
* For the purpose of the study, eczema meant itchy, red, dry, scaly skin lesions that appeared as “raised bumps” once or more in the past year. Parents were asked to report these lesions in their children by filling out a questionnaire.

Results/Key Findings
* Within the study population only 14 percent (90) children had clinically proven eczema.
* Children who did not own a dog in the previous four years, but tested positive for being allergic to dogs, had a four times higher risk of getting eczema. Children who owned a dog and also tested positive for dog allergy did not have a raised risk of eczema.
* Children who owned a cat before the age of 1 year and were allergic to cats had a higher risk of getting eczema. However those children who were allergic to cats and did not own a cat did not have a higher risk of eczema.
* Results also showed that introduction of eggs in the diet after one year did not protect against eczema.

Next steps/Shortcomings
Authors agree that this study fails to identify the reasons for the difference in results with dog and cat ownership, especially why dog ownership diminished, and cat ownership raised the risk of eczema. A relatively small group of children were included in the study. These children already had parents who suffered from allergies and this significantly raised their risk of being allergic. Authors suggest further studies that look into the molecular and genetic basis of such allergies and the interactions of these environmental and hereditary factors.

This study finds that children who have inherited the risk of allergic eczema are protected from the risk by owning a dog and placed at an increased risk by owning a cat. Also, delaying egg consumption to after 1 year did not protect a child from allergic eczema. Authors suggest that exposure to a dog early in life even in allergic individuals may lead to development of tolerance towards the allergy causing agent, called the antigen. They advocate owning a dog as a “natural form of immunotherapy” that modifies the deranged and hyperactive immunity in the child that causes the eczema in the first place.

For More Information:
Opposing Effects of Cat and Dog Ownership and Allergic Sensitization on Eczema in an Atopic Birth Cohort
Publication Journal: Journal of Pediatrics, 2011
By Tolly G. Epstein, MD, MS; David I. Bernstein, MD; University of Cincinnati, Ohio

*FYI Living Lab Reports Are Summaries of the Original Research.