Cleaning Yourself Sick?

Sterile environments may look harmless, but they may be endangering your health.



Roberta Warren has to work harder to stay healthy than most of us can imagine. This 35-year-old Larchmont resident has learned to dance around her severe allergies to trees, flowers, weeds, dust, mold, animals, and foods in a choreography that includes strict routines as well as an assortment of medications.

“I can’t dust unless I take Allegra and wear a mask,” Warren says. When she finishes dusting, she has to change her clothing and shower. Her mattresses have special covers to protect against dust mites. She rarely visits friends, unless she knows that they haven’t had pets in several years. When her three- and six-year-old children visit friends, they must change and bathe when they return to avoid exposing her to allergens from other people’s homes. Warren can’t go into her own finished basement without wearing a mask to protect her airways against the mold. Her motivation is simple: she is trying to avoid a life-threatening asthma attack.

She is hardly alone. Indeed, the Centers for Disease Control estimated that there were nearly 21 million cases of asthma in 2004, as compared with under 7 million cases in 1980, and reports from the World Asthma Meeting put the rate of increase in new cases between 20 and 50 percent every 10 years. Why the increase in asthma and other allergies? One theory, called the Hygiene Hypothesis, first proposed in 1989, posits that we’re cleaning ourselves sick. How? As we live in cleaner and cleaner homes (and offices and worlds), our bodies aren’t given the chance to acclimate themselves to a multitude of common, harmless microbes (and other microscopic substances from living organisms called antigens). Unaccustomed to these everyday particulates, our immune systems become more likely to react as strongly to them as to the varieties that are rare but much more deadly. In cases like Warren’s, something as harmless as household dust triggers asthma, an allergic reaction in the lungs that makes breathing difficult.

If the Hygiene Hypothesis is right, the result is an odd contradiction: our bodies, as Warren, unfortunately, is learning, could be in grave danger from the very systems that are supposed to protect it and all because those systems never learned how to tell the bad from the benign.

A Closer Look

Among the arsenal of weapons our immune systems have is a special classification of cells called “helper T cells.” Type 1 helper T cells, or T1 cells, help lead the fight against infections. T2 cells, on the other hand, play an important role in encouraging the body’s production of defensive proteins called antibodies. “A normal person has a good balance of both T1 and T2 and is not in excess of either,“ says Dr. Kira A. Geraci-Ciardullo of Allergy and Asthma Associates of Westchester in Mamaroneck.

The Hygiene Hypothesis says that if the T1s are not adequately stimulated when we’re young by exposure to certain common pathogens, then the immune system does not properly mature. Instead, there’s an overabundance of T2 cells, and the antibodies they help to promote can cause symptoms like redness, swelling, fever, mucus production in the respiratory tract, and airway constriction. In other words: allergies. These allergies broadly include hay fever, eczema, food allergies, and asthma. There’s even some evidence that this mechanism may play a role in autoimmune diseases, like multiple sclerosis and Crohn’s disease, in which the body attacks its own cells out of confusion.

Pass the Peanuts

Researchers have been able to isolate certain factors linked to rising rates of allergies and asthma, most notably the cleanliness of the area in which people are raised. For instance, populations from industrialized countries have higher rates of allergies than those from third-world settings. Additionally, when people from third-world countries immigrate to industrialized countries, the allergy rates among them rise. Why? No one knows for sure, but some believe that the nearly sterile conditions of the industrialized world mean that there are too few pathogens around to stimulate the T1s, and the result is allergies and asthma.

Just as with asthma, food allergies are on the rise worldwide. In the past decade, food allergies have doubled; according to the CDC, three million children under 18 years of age have food allergies, an 18 percent increase from 1997 to 2007. And children with food allergies are two to four times more likely to develop allergic conditions such as asthma.

To try to explain this, researchers at King’s College in London studied Jewish children in Great Britain and compared their peanut allergies to Jewish children growing up in Israel. In contrast to Israeli parents, British parents withheld nuts for the first year, but other dietary and cultural habits were the same. (The researchers purposefully used overlapping ethnic groups to try to screen out a cultural impact.) The results?

“Israeli children had less allergies to peanuts,” reports Dr. Rachel Koelsch, who specializes in allergy and immunology at the Cleveland Clinic. The rate of peanut allergies in Great Britain was 11 times what it was in Israel. Other studies have shown similar results for eggs and shellfish. American doctors previously thought avoiding contact with these foods would reduce allergies later in life. Now it seems that the opposite may be true. “We don’t recommend withholding specific foods anymore,” Dr. Koelsch says.

Food allergies, it seems, may be like dust allergies: early exposure in both cases is important in ensuring that the immune system later gives substances a pass.

Can You Be Too “Clean?”

Germs are everywhere. Every surface we touch could be contaminated with the season’s newest version of the cold or flu, and we want to protect ourselves. However, in our quest for clean, are we going too far?

Consider cleaning products. Many everyday cleansers contain active ingredients such as bleach and ammonium compounds. There is no question that these products kill bacteria and mold, but perhaps they’re killing too many bacteria and molds. Some experts say that using these products causes the same problem that the indiscriminate use of antibiotics causes. “The overuse of antibiotics may interfere with normal immune function,” says Dr. Geraci-Ciardullo. “It may alter the development of protective immunity.”

Dr. Koelsch explains: “Bacteria learn ways around antibiotics.” The medicine, in other words, becomes less effective the more we use it, because it “trains” the bacteria to withstand its presence. A number of household products, from clothing to cutting boards to children’s toys, now contain antibacterial chemicals, meant to kill germs on frequently dirty surfaces. Yet, these, too, contribute to resistance. These chemicals may do more harm than good by increasing the chances that resistant bacteria are growing in the home. “There’s no evidence that the use of these compounds improve the state of health” in a healthy household, says Dr. Stuart B. Levy, professor of Medicine and of Molecular Biology and Microbiology at Tufts University School of Medicine and president of the Alliance for the Prudent Use of Antibiotics.

What Should You Do?

In terms of household sanitizers and dealing with overtly dangerous microbes like salmonella or the influenza virus, Dr. Levy says that some cleaners can be used more safely than others. “I distinguish between those products that leave residues and those that don’t,” he says. Simple, single-ingredient products such as alcohol, peroxide, or bleach leave no residue. After these products dry, which usually takes seconds, they’re completely gone. As Dr. Levy notes, however, that with certain antibiotic chemicals like triclosan, they don’t evaporate completely and can leave invisible residues of their antibacterial chemicals. These chemicals then stay in the microbes’ environments, encouraging resistance by letting a number of successive generations adapt to the chemicals’ presence.

The best way to clean? Soap and water. Antibiotics in general should be reserved only for when they are truly needed. “We don’t want to alter our bacterial environment unnecessarily,” says Dr. Geraci-Ciardullo. “We can’t go to the extreme in trying to eliminate bacteria.”

Of course, it would be great if we could use the Hygiene Hypothesis not just to clean more intelligently but to help stop allergies altogether.

Striking a balance between clean and healthy is a fine line for Roberta Warren. She tries not to be a slave to her allergies. Curiously, she is not allergic to her dog of seven years, which she acquired before her allergies became problematic. She even manages to visit her family’s farm. Her allergies are manageable, as long as she takes a couple of Allegra before she leaves home. “If I’m equipped, I won’t end up in the emergency room,” she says. “I can still try to pretend I’m normal.”

Mary McIver Puthawala, an RN with a BS in Nursing, rests easy at night knowing that her family is well-protected against any danger from living in a home that is kept too clean.

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