Allergies in Dogs Linked to Those of Their Owners Through the Microbiota

According to researchers at the University of Helsinki in Finland, dogs are more likely to have allergies when their owners also suffer from allergic symptoms. It’s a curious correlation that raises questions.   In urban areas, allergies are more common—both in dogs and their owners—compared to those living in rural areas, suggesting that the environment plays a role. More specifically, the bacterial environment, which varies depending on the setting and lifestyle. In fact, the microbiota—whose composition varies from person to person—harbors microorganisms that live in symbiosis with us and play an important role in maintaining the balance of the immune system. The microbiota is to the immune system what a trainer is to a sports team. The presence of nonpathogenic bacteria, viruses, parasites, and fungi can thus specifically block the immune cells responsible for triggering allergies. Could it be, then, that allergies developed simultaneously by dogs and their owners have a common bacterial origin? However, the microorganisms beneficial to health differ between dogs and humans. In a new study, researchers sought to determine whether the occurrence of concurrent allergies was associated with gut or skin microorganisms shared between animals and humans. A total of 168 dog-owner pairs from rural or urban areas participated in the study. The results confirm that dogs and their owners who simultaneously suffer from allergic reactions tend to live in urban environments, appear to be exposed to the same risk factors for allergy susceptibility, and share the same skin microorganisms—but not gut microorganisms. The skin microbiota appears to be more susceptible to environmental changes than the gut microbiota, in both dogs and humans. It is, in fact, richer and more diverse in individuals living in rural areas compared to city dwellers. Yet it is precisely this microbial diversity that confers health benefits. Thus, for both dogs and their owners, the risk of developing allergic diseases is reduced when the skin microbiota is shaped by a rural environment and a lifestyle that promotes microbial abundance. Researchers have identified microbes associated with a higher risk of allergies—or, conversely, with a protective effect—in both dogs and humans. However, this predisposing or protective bacterial environment is not the same for both species, due to obvious physiological differences. It is therefore not so much the shared bacterial species that cause allergies, but rather a common risk factor: reduced microbiota diversity, which is responsible for a similar reaction in dogs and humans. This is something to consider before devising shared therapeutic strategies.