They say if you spend your time after school rolling around with a dog or stroking a cat you're less likely to become allergic to them.
Until now lots of people thought that if you play with pets you can catch germs from them and that's what makes you allergic.
Millions of kids in the UK suffer from asthma and other allergic conditions such as eczema, which have been linked to the fur of household pets.
Medicine from dirt
Doctors are now trying to find out if they can make a special kind of medicine from dirt that could also stop kids developing allergies.
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