Pets and Dirt Good for Child's Immune System

A feature story in the March 19, 2006 issue of USA TODAY reported that exposure to pets, peanuts and intestinal worms might actually be good for children, because they program their developing immune system to know the difference between real threats and common exposures.

The article begins by noting that this new thinking is opposite of the previous conventional wisdom that said it was best to protect children from these types of exposures. They now state just the opposite. Dr. Andy Saxon of the University of California-Los Angeles, states, "What we've learned is that it may, in fact, be important to be exposed early on to a sufficient quantity of allergy-causing substances to train the immune system that they are not a threat."

In the article Dr. Joel Weinstock of Tufts New England Medical Center added, "When you're born, Day Zero, your immune system is like a new computer. It's not programmed. You have to add software. Between the ages of zero and 12, you're learning to read, you're learning to write, and your immune system is learning to react to things. Part of that is learning to limit reactivity."

The article explains the new thinking on allergies by what is known as the "hygiene hypothesis". This hypothesis suggests that growing up in cities and suburbs, away from fields and farm animals, leaves people more susceptible to many immune disorders such as allergies and asthma. To strengthen this point Dr. Weinstock points to the difference between developed nations with urban communities and undeveloped, countries, "Hay fever is the most common allergy in the developed world," he says. "Yet, there are some countries in the world where doctors don't know what hay fever is."

The article added further evidence by reporting on a study by Dr. Dennis Ownby of the Medical College of Georgia. In his study Ownby followed 474 infants in the Detroit area from birth to age 7 at the Henry Ford Hospital in the hope of finding clues to why some would pick up allergies and others would not. The scientists on his team found that when they compared 184 children who were exposed to two or more dogs or cats in their first year of life with 220 children who didn't have pets, the children raised with pets were 45% less likely to test positive for allergies than other kids.

The article notes that this new thinking could have a profound effect and help millions. They report that more than 50 million people have allergic diseases, which are the sixth-leading cause of chronic illness in the USA. Additionally, they note that according to the National Institute of Allergy and Infectious Diseases (NIAID), costing the health system $18 billion a year.