Children who grow up with dogs are less likely to develop Crohn's disease later in life, a new study has found.
But the same cannot be said for cats, as felines do not protect young ones from developing the debilitating bowel syndrome.
Scientists at the University of Toronto found that exposure to dogs between the ages of five and 15 helps to build a strong gut lining and immune system - both of which protects from Crohn's disease.
Cats do not have the same gut-healing powers but researchers are unsure why this is.
They believe it may be because dog owners are more likely to live near green space.
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Both walking and living in a leafy area have previously been shown to protect people from the condition.
Growing up in a large family with three or more family members is also associated with a healthy gut later in life.
A health gut helps to protect people from Crohn's and a range of other illnesses, including colorectal cancer, diabetes and high blood pressure.
The study in Canada examined just under 4,300 people with Crohn's disease, who were enrolled in the Crohn’s and Colitis Canada Genetic, Environmental, and Microbial (CCC-GEM) project.
The questionnaire looked at age, the presence of household pets, the number of bathrooms in the house, living on a farm, drinking unpasteurised milk and drinking well water.
Researchers hope their findings may help physicians ask detailed questions about patients to better understand who is at the highest risk from Crohn's.
Senior author Dr Williams Turpin, of the University of Toronto, said: "Our study seems to add to others that have explored the 'hygiene hypothesis' which suggests that the lack of exposure to microbes early in life may lead to lack of immune regulation toward environmental microbes.
"We did not see the same results with cats, though we are still trying to determine why.
"It could potentially be because dog owners get outside more often with their pets or live in areas with more green space, which has been shown previously to protect against Crohn’s."
According to NHS figures, at least 115,000 Brits are living with Crohn's disease.
Symptoms include diarrhoea, abdominal pain and weight loss. Treatments currently aim to prevent symptom flare-ups through diet modification, medication and surgery.
The study findings were presented at the Digestive Disease Week 2022 conference in San Diego, California.
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