Phthalate Exposure and Allergy in the U.S. Population: Results from NHANES 2005–2006

BACKGROUND Environmental exposures to phthalates, particularly high-molecular-weight (HMW) phthalates, are suspected to contribute to allergy. OBJECTIVE We assessed whether phthalate metabolites are associated with allergic symptoms and sensitization in a large nationally representative sample. METHODS We used data on urinary phthalate metabolites and allergic symptoms (hay fever, rhinitis, allergy, wheeze, asthma) and sensitization from participants ≥ 6 years of age in the National Health and Nutrition Examination Survey (NHANES) 2005-2006. Allergen sensitization was defined as a positive response to at least one of 19 specific IgE antigens (≥ 0.35 kU/L). Odds ratios (ORs) per one log10 unit change in phthalate concentration were estimated using logistic regression adjusting for age, race, body mass index, gender, creatinine, and cotinine. Separate analyses were conducted for children (6-17 years of age) and adults. RESULTS The HMW phthalate metabolite monobenzyl phthalate (MBzP) was the only metabolite positively associated with current allergic symptoms in adults (wheeze, asthma, hay fever, and rhinitis). Mono-(3-carboxypropyl) phthalate and the sum of diethylhexyl phthalate metabolites (both representing HMW phthalate exposures) were positively associated with allergic sensitization in adults. Conversely, in children, HMW phthalate metabolites were inversely associated with asthma and hay fever. Of the low-molecular-weight phthalate metabolites, monoethyl phthalate was inversely associated with allergic sensitization in adults (OR = 0.79; 95% CI: 0.70, 0.90). CONCLUSION In this cross-sectional analysis of a nationally representative sample, HMW phthalate metabolites, particularly MBzP, were positively associated with allergic symptoms and sensitization in adults, but there was no strong evidence for associations between phthalates and allergy in children 6-17 years of age.