Children explore their environment using their senses of touch and taste. But recent flu seasons of epidemic proportions have led to health authorities imploring regular hand washing and the sanitizing of our homes and schools. And while infectious diseases are a legitimate cause for concern, some would argue that our society has gone overboard when it comes to protecting our kids from germs.
A mounting body of research suggests that exposing infants to germs may offer them greater protection from illnesses such as allergies and asthma later on in life. This line of thinking, called the “Hygiene Hypothesis,” holds that when exposure to parasites, bacteria, and viruses is limited early in life, children face a greater chance of having allergies, asthma, and other autoimmune diseases during adulthood.
Asthma is the most common chronic disease in the developed world. Initially, scientists blamed increasing air pollution for the surge in respiratory diseases. In the late 1990s, Dr. Erika Von Mutius, a health researcher, compared the rates of allergies and asthma in East and West Germany. Her hypothesis was that children growing up in the poorer, dirtier, and generally less healthful cities of East Germany would suffer more from allergy and asthma than youngsters in West Germany, with its cleaner and more modern environment.
What she found was exactly the opposite. Children in the polluted areas of East Germany had lower allergic reactions and fewer cases of asthma than children in the West. Dr. Von Mutius was forced to abandon her original hypothesis and rethink the question based on her new observations. Her new hypothesis, dubbed “The Hygiene Hypothesis,” is that children who are around numerous other children or animals early in life are exposed to more microbes, and their immune systems develop more tolerance for the irritants that cause asthma.
The “Hygiene Hypothesis” is supported by multiple epidemiologic studies demonstrating that allergic diseases and asthma are more likely to occur when the incidence and levels of endotoxin (bacterial lipopolysaccharide, or LPS) in the home are low. LPS is a bacterial molecule that stimulates and educates the immune system. It teaches the body to differentiate harmless substances from the harmful ones that trigger asthma. So, exposure to certain germs teaches the immune system not to overreact.
Because of those studies, scientists now know that the immune system is involved in far more than just allergies and asthma. Inflammation has been linked to many chronic adulthood diseases, such as heart disease, diabetes and Alzheimer’s. In a recent study, Dr. Thom McDade, director of the Laboratory for Human Biology Research at Northwestern University, found that children who were exposed to more animal feces and had more cases of diarrhea before age 2 had less incidence of inflammation in the body as they grew into adulthood.
More research is needed to understand exactly how childhood germ exposure might help prevent asthma. But Dr. McDade notes that, “Just as a baby’s brain needs stimulation, input, and interaction to develop normally, the young immune system is strengthened by exposure to everyday germs so that it can learn, adapt, and regulate itself.”