Need another reason to adopt a furry friend? Scientists have found that having pets can protect your kids from allergies and obesity.

A new study showed that babies from families with pets - 70 per cent of which were dogs - showed higher levels of two types of microbes associated with lower risks of allergic disease and obesity.

"There's definitely a critical window of time when gut immunity and microbes co-develop, and when disruptions to the process result in changes to gut immunity," said Anita Kozyrskyj, from the University of Alberta in Canada.

The latest findings come from the team's work on fecal samples collected from infants registered in a previous study which showed that children who grow up with dogs have lower rates of asthma.

The theory is that exposure to dirt and bacteria early in life - for example, in a dog's fur and on its paws - can create early immunity, though researchers are not sure whether the effect occurs from bacteria on the furry friends or from human transfer by touching the pets, said Kozyrskyj.

The study takes researchers a step closer to understanding the connection by identifying that exposure to pets in the womb or up to three months after birth increases the abundance of two bacteria, Ruminococcus and Oscillospira, which may reduce childhood allergies and obesity, respectively.

"The abundance of these two bacteria were increased twofold when there was a pet in the house," said Kozyrskyj.

Pet exposure was shown to affect the gut microbiome indirectly - from dog to mother to unborn baby - during pregnancy as well as during the first three months of the baby's life.

In other words, even if the dog had been given away for adoption just before the woman gave birth, the healthy microbiome exchange could still take place.

The study also showed that the immunity-boosting exchange occurred even in three birth scenarios known for reducing immunity.

The study suggested that the presence of pets in the house reduced the likelihood of the transmission of vaginal GBS (group B Strep) during birth, which causes pneumonia in newborns and is prevented by giving mothers antibiotics during delivery.