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The Hygiene Hypothesis: Is It Good to Be Clean?

Researchers in the U.K. found validation for the hygiene hypothesis: Kids kept "too clean" developed more atopy and asthma.

Data indicating that insufficient exposure to infection in early childhood predisposes children to the development of asthma and atopy (the hygiene hypothesis) have come largely from developing countries. As part of a longitudinal birth cohort study of 10,970 children, U.K. investigators examined the relation between hygiene and maternal report of infant wheeze and atopic eczema in the periods from birth to 6 months and from 30 to 42 months. Researchers created a simple infant hygiene score derived from a questionnaire administered when children were 15 months old to assess daily hand and face cleaning, hand washing before meals, and daily bathing.

Increases in the hygiene score were independently and significantly associated with development of wheezing and atopic eczema between 30 and 42 months of age but not during the first 6 months of life. For example, a 1-unit increase in the hygiene score was associated with a 4% increase in the odds of wheezing at 30 to 42 months of age. A second analysis indicated that maternal smoking during pregnancy, low maternal education levels, living in public housing, and greater use of chemical household products were independently associated with high hygiene scores.

Comment: Although these results have no immediate clinical applicability, the hygiene hypothesis has emerged as a possible explanation for the increase in allergic disease. Increasingly, parents are becoming aware of this hypothesis and are asking pediatricians about it. If this provocative hypothesis is proven to be true, the implications for hygiene practices in developed countries are enormous.

— Howard Bauchner, MD

Published in Journal Watch Pediatrics and Adolescent Medicine July 29, 2002

Citation(s):

Sherriff A and Golding J. Hygiene levels in a contemporary population cohort are associated with wheezing and atopic eczema in preschool infants. Arch Dis Child 2002 Jul; 87:26-9.

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Sherriff A and Golding J. Factors associated with different hygiene practices in the homes of 15 month old infants. Arch Dis Child 2002 Jul; 87:30-5.

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• Medline abstract (Free)