A study published in the British Medical Journal (May 22, 2004, Vol. 328, p. 1223) seems to support the idea that raising children in too sterile of an environment may contribute to allergies. Children who spent a lot of time with microbes (for example, children who live around pets or farm animals) are less likely to develop allergic rashes than children who do not have this exposure. This same benefit was not derived from getting infectious diseases such as colds and diarrhea. Infectious diseases seemed to increase the likelihood of developing rashes. Having a large number of siblings seems to protect against allergy, but if this study is right, it’s not because siblings pass on infectious diseases.