All across the world, the question of whether pets are good for a child’s health has been asked. There is not much consensus on the answer, unfortunately, however, there is consensus around the hygiene hypothesis—that a childhood devoid of germs entirely can lead to a less healthy child.
That’s not to say that all pet germs are good. Keeping a clean litter box for your cat and picking up after your dog are important. However, pet dander, pet-associated bacteria, or the amount of soil and particles kids come in contact with when they have pets may support the development of a healthier immune system.
On the other hand, a child’s health might have more to do with the lifestyle of families who choose to share their home with an animal. All of the research reported is self-selective. That is, the families who participated in the studies made their own decision about whether to have a pet and what kind. It could be that families who have pets are also more likely to spend time outside with their children or use fewer anti-bacterial products in the home.
To improve the reliability of the results, families would have to be assigned to have a pet or not in order to reduce this potential bias. This, of course, would not be a good idea for either the animals or the people involved.