Your allergies can trigger an asthma attack and one of the most common allergens is the good old household pet. That’s the reason some doctors advice families to get rid of the pet when a new baby comes along. Don’t do it. A new study indicates that children are more likely to have asthma at age 7 if in the first year of life

They received repeated courses of antibiotics, especially the newer broad spectrum types
They do not have a dog in the house.

This study looked at 13,000 children born in Manitoba, Canada, in 1995 and then followed up at age 7. This association was observed for antibiotics used in nonrespiratory infections. The risk of asthma was highest in children that received over 4 courses of antibiotics and in families without a dog or whose mother did not have asthma.

So, why would a dog help prevent asthma? It’s called the “hygiene hypothesis” of allergy or “germs are good for you”. This was first proposed by David P. Strachan in the British Medical Journal in 1989 to explain the observation that hay fever and eczema were less common in children from larger families. Part of our immune system uses a type of cell called Helper T cells. Depending on environmental exposures the Helper T cell develops into either Type 1 or Type 2 cells, each of which stimulates different parts of the immune system. These cells influence how our body responds to an infection in a variety of ways.

According to this theory, if we have a super clean body, a small exposure to an antigen (a molecule that stimulates an immune response) can drive these cells towards Type 2 and influence the immune system in such a way that we have more allergy related problems such as asthma, hay fever, and eczema. Bacteria and viruses elicit more of a Type 1 response and if the body is constantly exposed to germs our immune system is driven to a more balanced state between the Type 1 and Type 2 systems.

Antibiotics kill germs. Dogs bring germs into the home. According the lead author of this study, Dr. Anita Kozyrskyj, “Exposure to germs is lower in the absence of a dog. The administration of an antibiotic may further reduce this exposure and increase the likelihood of asthma development.”

This is just one more reason for all of us to limit the use of antibiotics.

That’s it for this week. Play hard, eat wise and I won’t need to see you at my office.