Allergies: Is Cleanliness at the Root of the Problem?

Allergies: Is Cleanliness at the Root of the Problem?

Get the dirt on what causes allergies and asthma

"Don't touch that, it's dirty!" Modern society doesn't like germs. In fact, we've become so obsessed with cleanliness that we go to great lengths to protect ourselves from germs with everything from antibacterial soaps and detergents to air purifiers. But does sanitizing our surroundings really make us healthier? Some experts believe that today's super-clean, relatively germ-free environments may actually increase our susceptibility to allergies, asthma, and other immune disorders.

Share Those Germs with Playmates
Research suggests that contact with certain germs and parasites early in life can be healthy for the immune system.

One study revealed that children who had several older brothers or sisters were much less likely to develop asthma, hay fever, or childhood eczema. It seems that by bringing home a variety of germs, the older siblings helped protect the younger ones from allergies. Another study revealed that children who were from small families but entered day care before the age of 1 year also were less likely to develop allergies compared with children who were older when they entered day care. Both studies suggest that when very young children regularly spend time with older children, whether at home or in another setting, it helps push their immune systems to protect them from developing asthma and wheezing later on.

Go Play in the Dirt with the Dog?
It's not only the typical minor bacterial and viral childhood infections that help keep some chronic ailments away. Some researchers suggest that time spent playing outdoors in the dirt and mud, which is filled with mycobacteria, serves a role in protecting children from later allergic and autoimmune diseases. This may explain the higher prevalence of asthma in the inner city, where kids are more apt to play on the concrete than dig in the dirt, and the low incidence of allergies in children who live on farms, where contact with soil is more common.

Having dogs and cats around during the first year of life may also help kids dodge disease. Research has shown that children growing up in households with two or more pets were 50% less likely to react to allergens in the future compared with children growing up without pets. These allergens included not only cat and dog dander but also molds, grasses, and other common allergens.

Bacteria Aren't All Bad
Although some bacteria can cause disease, not all strains of bacteria are dangerous. A considerable number of bacteria within our intestinal tract are vital to a healthy existence. More and more researchers suspect that lack of exposure to some types of germs can weaken some parts of the immune system, while allowing other parts to develop unchecked. This theory, known as the hygiene hypothesis, blames the modern preoccupation with cleanliness for contributing to the rise in the incidence of asthma and allergies. To grasp this theory, it's helpful to understand a little about how our immune system develops and functions.

The Immune System Needs Germs to Grow
The main role of the body's immune system is to distinguish between harmless and harmful organic matter and a few poisons. One part of the human immune system comes hard wired at birth, while another part develops as we grow, honing the ability to recognize and defeat microbial intruders with antibodies. This latter part has two major branches, each active against a different set of microbes.

When these two branches are in balance, the immune system steers a healthy course between two extremes: allergies such as hay fever, eczema, or asthma at one end and diseases such as rheumatoid arthritis, juvenile (type 1) diabetes, or multiple sclerosis on the other end. But if the system veers too close to one side or the other, the risk of developing one such disease or medical condition increases. This balance typically develops in the first few years of life.

Proponents of the hygiene hypothesis suggest that how well this system is tuned depends on the kinds of microbes to which the two branches of the antibody-making immune system get exposed. Because modern life greatly limits children's exposure to microbes that exercise one side of the system, their immune system fails to balance properly. Therefore, the body continues to treat everyday irritants, such as dust and pet dander, as if they were dangerous parasites.

What Now?
The hygiene hypothesis is still being researched, debated, and refined. But if the hygiene hypothesis holds up, what can we do to avoid immune disorders? Lessening our obsession with hygiene might help, but this could also lead to more colds and infections that do not reduce asthma and allergy risk.

Researchers have begun to explore vaccines and probiotic treatments that may help prevent asthma and other allergic reactions. So if we don't meet enough microbes in the course of everyday life, we may have to deliberately undergo exposure to them in order to properly train and balance our immune systems. Until these options are developed further, consider going easy on antibacterial products, and use plain old soap and water instead. Also, try to relax a bit more about playing in the dirt, whether it's your child in the mud or you in the garden. It might just help strengthen your immune system and improve your overall health.

Medically reviewed in February 2020.

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