The hygiene hypothesis is a proposed explanation for why some cultures are having drastic rises in the rates of atopic dermatitis, childhood asthma, and allergies. It is a theory about what causes eczema. A child’s immune system develops antibodies as it learns to react to substances in the environment.

The basic understanding of what causes eczema starts with an inherited sensitivity of the immune system. Eczema, asthma, and allergies are caused by an oversensitivity of the immune system to substances in the environment. The substances that trigger the eczema, asthma, or allergic response are called allergens. The inherited condition of a sensitive immune system is called atopy.

The hygiene hypothesis claims that by restricting a child’s exposure to substances, viruses, and harmless bacteria in the environment, the child’s immune system may fail to learn to respond appropriately to these substances. The popular use of anti-bacterial products and a striving towards creating a sterile environment can restrict the substances to which children’s immune systems learn to react normally. Therefore, without normal exposure to dirt and germs, the child’s immune system may not be as capable to recognize harmless substances as harmless. It causes the immune system to overreact.

Some further investigation has been done since the initial development of the hygiene hypothesis. The result of living without normal exposure to germs is that the immune system does not get appropriately deactivated by harmless substances. This over-reactive immune system connects to a link between asthma, eczema, and allergies with immune diseases, insulin dependent diabetes, irritable bowel syndrome, and ulcerative colitis. Some research has provided evidence that exposure to infections and disease-causing agents causes less atopy.

The hygiene hypothesis is just that, a hypothesis. It may be an accurate description of what causes eczema in some families. However, many doctors think that the opposite is true. The counterpoint is that some childhood infections may trigger eczema, therefore protecting them from germs decreases their risk of eczema.

There are still many questions about what causes eczema that need to be answered. Without a better understanding of how eczema develops and how allergens cause eczema, theories on causes of eczema are just educated guesses. However, the movement towards obsessive cleaning and use of bleach and anti-bacterial products may actually be harmful or at least not as helpful as once thought. Parents may want to think twice about frequent use of anti-bacterial products and obsessive cleaning.