Children brought up with animals, and youngest children in families, are often the least likely to get asthma,  and this may be down to the microbiome (all the bacteria) in the home’s house dust. Mice fed house dust from homes with dogs were more likely to be immune to respiratory syncytial virus (RSV) than mice fed with dust from non-dog homes. RSV is a common childhood infection, and children exposed to it are more likely to get asthma.The microbes in their gut were also different.

The hygiene hypothesis suggests that we get more allergies now because our immune systems don’t have enough to do. Hookworms might be able to cure allergies – but a dog is much more fun to take for a walk!