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

The article in the NEJM starts off 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."  The article in JAMA 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." 

What both these articles are saying is that it is a needed part of development for children to be exposed to certain amounts of germs and other irritants in order for their immune systems to develop properly and give adequate protection later in life. In the study, children from parts of Austria, Germany, and Switzerland where there were both farming and non-farming households were studied.  The investigators related the level of exposure to endotoxin (such as dust and germs), determined by sampling dust from the mattresses where the children slept, to the prevalence of asthma and other related conditions. The greater the endotoxin exposure, the less likely it was that children had asthma.

These findings are completely opposite of what most doctors were telling their patients over the past several decades.  The results of the study showed that just 3 percent of farm children had the common type of asthma known as atopic and 4 percent had hay fever. In non-farming households, 6 percent had atopic asthma and almost 11 percent hay fever. This showed that exposure to farming in the first year of life was especially protective. In the U.S., the asthma rate rose about 74 percent between 1980 and 1996 but decreased slightly by 1999, the most recent year available, according to the Centers for Disease Control and Prevention. About 10.5 million Americans have asthma, and 24.8 million have hay fever.

These findings, combined with similar findings from other studies, have borne a whole new type of thinking and theory.  The theory is known as the "hygiene hypothesis". It holds that early contact with some germs arms the maturing immune system against some allergic conditions.  Some research, in fact, has suggested that children who are exposed early on to pets or to lots of other youngsters at day care are less likely to get colds or allergies later on. Supporters of the new theory suspect that indoor plumbing, cleaner and more airtight homes, and antibiotics have contributed to an explosion in allergies in industrialized countries.