A 2023 Psychology Today article sites two studies, each indicating that a child raised with pets during the first two years of life reduces the likelihood of asthma.

"A substantial body of research has been published which shows that exposure to a dog or a cat while an individual is young actually serves to prevent the onset of asthma and allergies."

Yu Taniguchi of the National Institute for Environmental Studies in Japan, surveyed 4317 individuals. Of these 2030 were dog and/or cat owners and 2287 were non-pet owners. What they found was surprising. The numbers showed that of the pet owners' children there were 50% less with asthma than of the non pet owners' children.

"The risk of a child developing asthma was actually cut in half if they grew up living with a dog or a cat."

Another study, this one in Sweden, by Bill Hesselmar of the Department of Paediatrics at the University of Gothenburg, involved two separate groups. In the first group were 1020 children aged 7 to 8 years. The second group tracked 249 children from birth to age 8 or 9. Both groups were assessed and systematically tested for allergy and asthmatic symptoms over that time span. The study found that a child living with pets during their first year of life, reduced the likelihood that asthma would develop. It also showed that having a pet further reduced the risk that the children would develop a broad range of other environmental allergies as well. To top it off, the more pets the child grew up with, the more resistance to allergens that child became.

/https://www.psychologytoday.com/us/blog/canine-corner/202303/living-with-a-pet-reduces-the-risk-of-asthma-in-children