Phipatanakul W, Celedon JC, Raby BA, et al. Pediatrics. 2004;114:13–18
Purpose of the Study.
To examine the relationship between endotoxin exposure early in life and eczema during the first year of life in children with parental history of asthma or allergy.
A birth cohort of children in metropolitan Boston, Massachusetts, selected for a history of allergy or asthma in at least 1 parent.
A total of 505 infants from 499 Boston families were enrolled between September 1994 and August 1996 and followed prospectively. Seven children followed for ≤4 months were excluded from analysis. Adequate analysis of endotoxin was obtained from house dust sampled from 401 living rooms. Endotoxin exposure was categorized into quartiles by concentration of endotoxin units per milligram of house dust (EU/mg). Potential predictors of eczema and confounders were considered for multivariate analysis including socioeconomic data, birth weight, maternal age, season of birth, breastfeeding, ingestion of allergenic foods, family history of atopic diseases, pets in the home, and day care. Maternal serum was analyzed for allergen-specific IgE to several common allergens. Every 2 months the primary caregiver was asked, “Has a doctor or nurse ever said that your child has eczema?”
Of the 498 children, 140 (28%) had eczema in the first year of life. Exposure to high levels of endotoxin (80.48–713.2 EU/mg) at 2 to 3 months of age were inversely associated with eczema during that time. For every quartile increase in endotoxin measured in living room house dust, there was a decrease in the odds of developing eczema in the first year of life (odds ratio [OR] for each quartile increment: 0.76). Exposure to a dog in the home at 2 to 3 months of life compared with no dog exposure decreased the odds of having eczema in the first year of life by half; however, this association became less significant when adjusted for endotoxin exposure. In the multivariate analyses, paternal history of eczema (OR: 1.91) and maternal sensitization to at least 1 allergen (OR: 1.61) were associated with developing eczema.
In children with parental history of asthma or allergy, exposure to high levels of endotoxin at 2 to 3 months of age may protect against eczema development in the first year of life. Additionally, both paternal history of eczema and maternal sensitization to ≥1 allergen are associated with increased risk of eczema in the first year of life.
A great deal of faith has been placed in the “hygiene hypothesis” being correct despite relatively few prospective birth cohort evaluations. Although previous studies have focused on allergic sensitization, cytokine production, and development of asthma, this study makes an association between endotoxin levels in the living rooms (but not bedrooms) of children’s homes and the development of eczema in the first year of life. This lends another facet, and end-organ effect, to support the argument to validate the hygiene hypothesis. Additional data from this and other high-risk birth cohorts will provide additional data to fuel this debate.