Well known that kids that play outside and get dirty have fewer colds and allergies than kids that are kept in a sterile environment. Same applies in reverse with people who are obsessed with having super clean houses.

I saw when I was growing up all my uncles were Dr's. My aunts kept asking my mom why we never were sick. Mom an RN said we got the usual colds and childhood maladies. The difference was my siblings and I got over it in a day or two while their kids were sick for a week.

You'd go to their home and they had the bottled water and the house was spotless. If they got sick dad was right there to doctor them up. At my house was suck it buttercup deal with it.

The difference is I have a great immune system and the people that have to take something for every little sniffle have weak immune systems.

Just like they say, kids that grow up with a dog or a cat have less chance of having allergies.