Health Library

A study done in Europe provides evidence that children’s immune systems work better when they are exposed to germs, dust, and dirt at an early age. These findings were published in the September 19, 2002 issue of the New England Journal of Medicine (NEJM) and the August 28, 2002 issue of the Journal of the American Medical Association (JAMA).

The NEJM article begins by stating, “It is known that children of elementary-school age who live on a farm are less likely to have asthma than their counterparts from nonfarming households.” Similarly, the JAMA article states, “Exposure to 2 or more dogs or cats in the first year of life may reduce subsequent risk of allergic sensitization to multiple allergens during childhood.”

Both articles suggest that it is essential for children to be exposed to certain amounts of germs and irritants as part of their development, which helps their immune systems mature and provides better protection later in life. The study involved children from parts of Austria, Germany, and Switzerland, where there were both farming and non-farming households. Investigators examined the children’s level of exposure to endotoxins (such as dust and germs) by sampling dust from the mattresses where the children slept. They found that the greater the endotoxin exposure, the less likely the children were to have asthma.

These findings are contrary to what many doctors advised their patients in past decades. According to the study, just 3% of farm children had atopic asthma, while 4% had hay fever. In non-farming households, 6% had atopic asthma, and nearly 11% had hay fever. The results indicated that exposure to farming in the first year of life was particularly protective. In the U.S., the asthma rate rose about 74% between 1980 and 1996 but decreased slightly by 1999, according to the Centers for Disease Control and Prevention. Approximately 10.5 million Americans have asthma, and 24.8 million have hay fever.

These findings, combined with similar studies, have led to a new line of thinking known as the “hygiene hypothesis.” This theory suggests that early contact with some germs strengthens the maturing immune system against certain allergic conditions. Some research has even suggested that children exposed early on to pets or to many other youngsters at daycare are less likely to develop colds or allergies later in life. Proponents of this theory believe that indoor plumbing, cleaner and more airtight homes, and antibiotics have contributed to a rise in allergies in industrialized countries.