But lately the research has shown the opposite- and that having a pet may even have a protective effect.
If you have a new baby at home, having a furry friend might just keep that baby healthy.
A new European study looks at nearly 400 infants. They found that kids who had a dog around for their first year of life were not only healthier overall, but had fewer respiratory infections than kids without a dog. Cats provided similar benefits to babies, but not as much as the dogs.
"They have less respiratory infections, less runny noses, less antibiotics, less visits to the doctor in that first year of life," said Dr. Emma Raizman with Cleveland Clinic.
Researchers say that animal contact may help an infant's immune system mature faster, helping them fight off common viruses during early childhood. Pediatricians say the findings may provide comfort to new parents.
"This article really shows that in that first year it can actually be a good thing to have them both together. Now, you always want to make sure for safety reasons you never leave your baby alone with your dog, but when it comes to the immune system, having a dog in the home can help with that," adds Dr. Raizman.
This study only followed the babies for a year so it doesn't prove that the benefits are long lasting.
But other studies have found a long term benefit that kids with pets have a lower chance of developing allergies later in life.
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