An international study found that early exposure to pet dogs may reduce the risk of atopic eczema in children who are genetically predisposed to the condition. The research suggests that having a dog in the home during the first months of life can offer protection against the development of the common skin condition.
The study evaluated 24 genetic variants associated with eczema and 18 environmental factors, including pet ownership, breastfeeding, and maternal smoking. Researchers performed an initial analysis on more than 25,000 individuals, which indicated an interaction between seven environmental factors—such as having pets—and at least one genetic variant linked to eczema. This analysis was expanded to include genetic and environmental data from nearly 300,000 people, revealing 14 interactions related to the development of eczema.
The most notable association was found between a specific genetic variation near the interleukin-7 receptor gene (IL-7R) and having a dog in the household. Laboratory experiments confirmed that interaction with dogs can alter the expression of the IL-7R gene in the skin, leading to a reduction in skin inflammation. The IL-7R is known to be involved in immune cell function and inflammation, which are key factors in the development of eczema.
"We know that genetics affects the risk of eczema in children, and previous studies had already shown a protective effect of dogs, but this is the first study to explain the molecular mechanism behind it," said Professor Sara Brown of the University of Edinburgh's Institute of Genetics and Cancer. "More work is needed, but our findings mean we have a chance to intervene in the rise of allergic disease, to protect future generations," she added.
The mechanism behind the protective effect of dog exposure appears to involve the training of the immune system. Scientists suspect that being exposed to a broader range of microbes early in life, whether from dogs or older siblings, may help the immune system learn to react appropriately rather than excessively. This could explain why early-life dog exposure is associated with a lower prevalence of atopic eczema among genetically at-risk children.
Dr. Marie Standl of the Helmholtz Center in Munich noted the importance of personalized prevention strategies. "Not all preventive measures work for everyone—and that's why studies on the interaction between genes and the environment are fundamental. They help us move closer to more personalized and effective prevention strategies," she said.
However, experts advise caution. The protective effect of having a dog is not universal, and introducing a dog into a family with children who already have eczema could potentially worsen symptoms. Allergy specialists have warned that if a child already has eczema, having a pet dog at home might exacerbate the condition. The researchers emphasized that their study focused on the prevention of eczema, not its treatment, and did not analyze the effect of dog exposure on existing cases of the condition.
The research team also noted that the same benefits of reduced eczema risk did not extend to cat ownership. The environmental factors studied included pet ownership, whether individuals were breastfed, and whether they had siblings, among others.
Atopic eczema is a common skin disorder characterized by dry, itchy, and inflamed skin. It is caused by a combination of genetic and environmental factors, but little is known about how these elements interact in the development of the condition. The findings of this study provide new insights into what could cause eczema in children, potentially opening new avenues for prevention.
The researchers acknowledged the need for further studies, particularly involving more diverse populations. The participants in this study were exclusively of European white descent, so additional research is necessary to determine if the protective effect of early-life dog exposure on eczema risk is valid in other ethnic groups.
Professor Brown emphasized the importance of continued research in this area. "The most difficult questions I'm asked by parents in clinic are about why their child has eczema, and how they can help," she said. "Our findings offer a potential way to reduce the risk of eczema in children, but it's crucial that we understand how this applies to different populations around the world."
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