I know a woman who is a clean freak. All her bathrooms are stocked with antibacterial soaps, and her surfaces get washed with bleach-infused cleansers and other harsh chemicals. Even the basement and garage get this treatment. She created a fenced-in area in her backyard that she filled with sanitized sand for the kids to play in. Both kids were given antibiotics at the slightest sign of a cold or sniffle. The irony, though, is that in spite of her efforts to slay every last germ that might have caused illness, her son developed asthma and her daughter grew up to have severe allergies. Is it possible that her fanatical cleanliness might have backfired?
The answer is yes, according to a recent study led by Thom McDade, PhD, associate professor and director of the Laboratory for Human Biology Research at Northwestern University. Dr. McDade’s team found that exposure to parasites, bacteria, and viruses early in life is precisely the type of stimulation that the young immune system needs so it can learn, adapt, and regulate itself. Without having this exposure, children face a greater chance of developing allergies, asthma, and other autoimmune diseases when they become adults. In other words, too much cleanliness makes the system more vulnerable to serious conditions down the line. According to Martin Blaser, MD, professor of internal medicine at New York University, “Microbes ‘…perform important physiological functions but because of modern life they are changing and some are disappearing. Those disappearances have consequences — some good, some bad.”
In fact, Dr. McDade’s team found, among other things, that children who had more exposure to animal feces and more incidence of diarrhea before age two had a reduced incidence of inflammation in the body as they grew into adulthood. Says McDade, “”We’re moving beyond this idea that the immune system is just involved in allergies, autoimmune diseases, and asthma to think about its role in inflammation and other degenerative disease. Microbial exposures early in life may be important…to keep inflammation in check in adulthood.” Inflammation plays a key role in triggering chronic diseases such as diabetes, heart disease, and Alzheimer’s.
But why does exposure to germs early in life seem to have this protective effect? Experts attribute it to something they’ve given the colorful appellation, “the hygiene hypothesis.” The hygiene hypothesis was first espoused more than 20 years ago by David P. Strachan, a professor of epidemiology at St George’s Hospital Medical School in London. His colleague, Marc McMorris, M.D., a pediatric allergist at the University of Michigan Health System, explains, “We’ve developed a cleaner lifestyle, and our bodies no longer need to fight germs as much as they did in the past. As a result, the immune system has shifted away from fighting infection to developing more allergic tendencies.”
Essentially, the hygiene hypothesis holds that our greater reliance on antibacterial products, the use of airtight windows and doors, the smaller size of the modern family, and the use of vaccines and antibiotics have all reduced our bodies’ exposure to germs and infectious diseases. This essentially has left the immune system unemployed, and to paraphrase an old maxim, “idle immune cells are the devil’s tool.” The immune system is also designed to recognize foreign substances as allergens, and without bacteria to combat, it goes to town “creating” allergic conditions and inflammatory responses to irritants — just to keep busy.
An article on the FDA website says, “The “hygiene hypothesis” is supported by 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 by triggering signals through a molecular “switch” called TLR4, which is found on certain immune system cells.”
Not everyone agrees that the hygiene hypothesis has validity. Since the theory says that exposing kids to allergens and microbes early on will avoid problems later, some point to a study of risk factors for asthma in inner city children that found that the inner city kids who had early exposure to allergens and germs still developed asthma at the same rate as children not exposed. Of course, the critics perhaps fail to consider that other factors peculiar to the inner city environment might increase asthma risk anyway, such as increased air pollution, increased stress, increased exposure to vermin (rats and roaches), less opportunity for recreation, and so on.
In any event, the situation creates a bit of a conundrum. Naturally, parents want to protect their kids from scary infectious diseases, but how can they on the one hand protect them from infection while at the same time allow them enough exposure so that the kids don’t later develop allergic conditions and systemic swelling?
Perhaps the answer is to just let kids be kids. If your kid picks up a piece of food from your floor and sticks it in her mouth, don’t freak out — assuming you clean the floor occasionally. If she comes home muddy, don’t whip out the antibacterial soap, which not only wipes out germs but also screws up the environment and puts the entire family’s health at risk from chemical exposure. In short, cleanliness may indeed be next to godliness, but being overzealous may play the devil with your health.