There is a theory, known as the 'hygiene hypothesis' which suggests that an environment that is too clean in the early years can be bad for a child's health.
It is backed up by research from Warwick University, which found that having a cat or dog exposed children to more infections early in life, which in turn boosted their immune system.
Having a pet can also help improve your child's fitness; children play more actively once they have a pet, according to a study carried out for Masterfoods.
Bringing a pet into the home can also make children more friendly, caring and relaxed, says Dr June McNicholas, a specialist in Human Animal Companion Bond research.
However, pets can also pose health risks to children, one of the biggest being the roundworm toxicara canis which infects dogs and can cause eye damage.
Avoid problems by make sure your pooch is wormed regularly, and wash your childs hands after playing in the garden, sandpit or parks where dogs are allowed.