How a Dog Can Protect a Newborn from Forming Allergies

Bacteria is generally good for us. In fact, we wouldn't be able to live without the massive amount of bacteria in our stomach--ten bacteria cells per one human cell.* Research published by the Journal of the American Medical Association suggests that having two dogs or cats in close proximity to an infant introduces bacteria that can reduce the infant's chances of forming allergies by 55%. The study also found that the same pets can reduce the likelihood of indoor and outdoor allergies by 48%. Essentially an introduction of a wide variety of bacteria at a young age can significantly decrease our likelihood of having an allergic reaction to bacteria that is simply neutral to our body's livelihood.

The reason is, albeit, a little bit gross, but no less interesting. Dogs and Cats track in dirt from the outside and get saliva on many of a home's surfaces. This dirt and saliva contains a wealth of bacteria cultures ranging from dog specific bacteria to pollen and hundreds of thousands of others.^‡ These cultures get transmitted to the infant through its natural urge to put everything in its mouth.

Once the bacteria has entered the infant's body, it comes in contact with white blood cells, and defensive proteins such as NLRP7.^† These tag each different kind of bacteria and observe them to see if they will be good, neutral, or bad for the body. Once your white blood cells have categorized the bacteria it will remember what threat level that cell is, and react accordingly next time it comes into contact with that cell.

Interestingly our white blood cells lose much of this ability later in life, which is part of the reason some people go into anaphylactic shock after being stung by a bee. The body overreacts to what is actually a low level threat. This is also the reason why we form allergies later in life; our white blood cells do not wait to see what a particular bacteria will do, it just sees that it has not been categorized and treats it as a high-level threat.

So, while it is a little gross, maybe it isn't so bad when your dog licks your infant. For that matter maybe it isn't quite so bad that your infant puts everything in its mouth. It's just your child's instinct, and, at least in this case, instinct may work towards the infant's benefit.