Emma Donahue, 2, enjoys life on her family's farm. She loves to touch the menagerie of animals and pick up the feathers and other "treasures" they leave behind. "I'm not the type to get stressed out over dirt. That takes a lot of the fun out of being a kid," says her mom, Stacey, of Lithia, FL. "I just tell Emma not to put her hands in her mouth until we can wash up."
Emma's early exposure to old-fashioned muck, with its cornucopia of germs, may be just what the doctor ordered, at least according to the "hygiene hypothesis" and a growing number of studies that support it. The crux of the theory: The modern war on germs may have gone too far, wiping out too many of the good guys along with the culprits that cause diseases. Exposure to certain bacteria in the first years of life is crucial for teaching the developing immune system to recognize friend from foe. Without this early training, the imbalance within the body's immune cells may predispose them to attack a host of harmless substances, such as cat dander and pollen, or even other cells in the body.
That immune-system immaturity may be a major contributor to one of the most perplexing public-health problems our country faces: the increasing number of kids who are suffering from childhood allergies, asthma, and eczema. "The hypothesis is a leading theory to explain things like rising rates of these illnesses," says Richard Johnston, M.D., a member of the Institute of Medicine and a pediatric immunologist at the University of Colorado School of Medicine, in Denver. Many experts are also investigating possible links to adult autoimmune diseases, such as diabetes, multiple sclerosis, and lupus.
It's time to rethink our efforts to wipe out every microbe that comes near us. Some of those germs might actually be good for our kids.
"Part of the problem comes from our belief in the myth that we would want to live in a germ-free world," says Graham Rook, M.D., an immunologist at the Royal Free and University College Medical School, in London. "Lab animals raised in a genuinely sterile environment develop abnormal immune systems." Indeed, a typical adult human houses trillions of bacteria in his intestines. These normal gut "flora" aid digestion, produce such nutrients as vitamin K and certain B vitamins, and play a long-recognized but little-understood role in the operation of the immune system.
Even our skin is replete with harmless bacteria so deeply embedded you could never scrub or sanitize them away. Nor would you want to: These skin germs serve as a barrier against harmful stray bacteria that might otherwise take up residence there.
Of course, no one is claiming we shouldn't protect ourselves against illness. Or return to the days before water treatment, antibiotics, and vaccinations largely wiped out scourges like cholera, tuberculosis, and polio. "Rather, we're recognizing that in the process of sanitizing our modern environment, we've taken away something that the immune system needs to program its early development," says Dr. Rook.
Scientists aren't yet certain how the process works, but they believe specific microbes switch on cells that then suppress a reaction against allergens and beneficial bacteria. They point to numerous studies that show that allergies and asthma occur less frequently among children who:
- have older siblings (think walking germballs)
- spend time in daycare in the first year or two of life
- have early exposure to pets or farm animals
- live in rural parts of the country or in areas of the world that lack modern sanitation.
The good news: The organisms that babies and toddlers need to encounter in daily life to develop healthy immune systems aren't the kinds that make us sick. Instead, the common denominator among older siblings, daycare, animals, and rural environments appears to be the largely harmless bacteria found in dirt, mud, puddles, and ponds.
The hundreds of antibacterial products flooding the market each year, in everything from hand gel and soap to toys and even sneakers, may be making the problem worse. "If our past experience with overuse of antibiotics is any guide, these items could do more than eliminate good germs," says Tufts University microbiologist Stuart Levy, M.D., author of The Antibiotic Paradox. "They're likely to encourage bacterial resistance to these products and to antibiotics."
Some of those newly resistant bacteria could cause illness. Echoing Dr. Levy's concerns, the American Medical Association recently urged government regulators to speed their review of antimicrobial agents in consumer products to determine whether they actually pose a threat. (Manufacturers of these products defend them as beneficial, pointing out that they can kill or inhibit the growth of bacteria, including salmonella and E. coli, that cause intestinal illnesses, skin infections, and other unpleasant—and in some cases fatal—diseases.)
The alarm first sounded in 1998, when researchers at Tufts University discovered that triclosan, the active ingredient in most antibacterial cleansers, works more like an antibiotic drug than a disinfectant. Instead of obliterating bacteria and then evaporating (like bleach), triclosan blocks a specific enzyme that germs need to survive. The trouble is, microbes are infamous for developing ways around such narrow modes of attack. Triclosan also lingers on such surfaces as tubs and kitchen counters for days, even weeks, which gives bacteria plenty of time to develop resistance.
While critics counter that no one knows whether any of this poses a real problem, many microbiologists believe that it's not worth taking the risk, especially given that the only place triclosan and other similar products have been proven to reduce the spread of illness is in hospitals, where workers scrub their hands and douse surfaces for 5 to 20 minutes, not the mere seconds most people spend on such activities.
A Healthier Kind of Clean
So what should you do to give your child's immune system a head start, without going overboard? Experts—even those who aren't sold on the hygiene hypothesis yet—agree that taking the following easy steps is wise:
Widen your circle
If your child's not in daycare and doesn't have an older sibling, make sure she still has lots of contact with other kids and their germs. You might join a playgroup or sign her up for Mommy and Me classes once or twice a week. But don't purposely expose her to people who are sick. Those are not the type of bacteria she needs.
Don't relegate your pet to the backyard
It's fine to have a gentle pet in the same room with your baby. (But not if your child's already developed an allergy to animals. In that case, isolating the pet from bedrooms, or even finding it a new home, may be called for. Once an allergy develops, exposing a child to the allergen only makes things worse.)
Because good bacteria are found in soil and natural bodies of water, families who enjoy gardening, camping, a day at the lake, or trips to the country shouldn't be shy about including their youngest one in the fun.
Stick with your tried-and-true cleaners
The best antibacterials are the old-fashioned ones, says Dr. Levy. That includes bleach water (one cup chlorine bleach to one gallon water), cleansers (like Comet or Bon Ami), alcohol (either isopropyl or ethyl alcohol), or hydrogen peroxide. It's also smart to open windows to bring in fresh, clean air.
Recent warnings about the dangers of triclosan have spurred new antibacterial cleaners and lotions labeled "alcohol- and triclosan-free." But take care: These often use triclosan's close cousin, triclocarban, a compound that is thought to work in essentially the same way, so check the ingredients. If you must use these or other antimicrobial products, do so sparingly—only when cleaning up after cutting raw meat or poultry, for example, or if someone living in the house has a medical condition that leaves him susceptible to infection.
Don't encourage germophobia
Of course, parents mean well when they disinfect playground equipment or insist that kids stay away from yucky, dirty mud. But doing so may pass on some unnecessarily scary ideas about the world. Instead, try to give your child the freedom to explore his environment, then matter-of-factly tell him when it's time to wash up. If he starts refusing to touch things, washing excessively, or asking fearful questions about dirt and grime, look hard at the message you're sending. It may be that in the end, the best way to give our kids a healthy attitude about germs—as well as a strong immune system—is by trying not to protect them too much.