This article suggests that exposure to microbes in early life helps develop a child’s immune system. Speaking of dietary habits among 18th-century “Scotch-Irish” immigrants to the back-country regions of colonial America, David Hackett Fischer notes in Albion’s Seed (1989, Oxford University Press): “The quality of butter was believed to be improved in proportion to the number of human hairs embedded in it. ‘The mair dirt the less hurt,’ Appalachian housewives liked to say.” Perhaps they were on to something.

John Derbyshire
Huntington, N.Y.

We originally reviewed the inverse relationship of febrile infections and asthma nearly 40 years ago. However, it’s not possible to explain the current increase in the prevalence and the morbidity of asthma simply on the basis of “more infections . . . less asthma.” Infantile atopic eczema often precedes the onset of the respiratory problems. Neither genetic nor environmental-dietary factors can adequately account for that or the fact that childhood allergy, almost nonexistent one or two generations ago, has become such a universal problem. The question has been raised whether health-care practices (such as immunizations and overzealous administration of antihistamines, antibiotics, and antipyretics) play a role in this respect. Are we practicing physicians, like the ancient Theban king Oedipus, responsible for the plague we’re trying to resolve?

Constantine J. Falliers
Denver, Colo.