PURPOSE OF THE STUDY.
To evaluate the effect of environmental exposures and allergic sensitization on the risk of developing eczema at 4 years of age.
This was a birth-cohort study that enrolled newborns in the Cincinnati metropolitan area born between 2001 and 2003. Enrolled infants had at least 1 parent with symptoms of asthma, allergic rhinitis, or eczema.
On a yearly basis from the ages of 1 to 4 years, children underwent a physical examination, a clinician's assessment, and a skin-prick test (SPT) to 15 aeroallergens plus cow's milk and hen's egg. Parents completed an in-person validated survey at these times to assess environmental exposures and the parent's perception of their child's eczema. A home environmental assessment and collection of house dust samples were performed before 1 year of age.
Of the 636 children analyzed, 14% had eczema. The most significant predictors of eczema at age 4 were having a parent with eczema (P = .03), a positive SPT result to egg at 1 year of age (P < .001), and a positive SPT result to elm tree pollen at ages 1, 2, or 3 years (P = .03). Those who owned a dog before the age of 1 and were SPT-positive to dog at age 1, 2, or 3 did not have an increased risk for eczema at age 4, whereas those who did not own a dog before age 1 and were SPT-positive to dog at age 1, 2, or 3 had an almost fourfold increased risk of eczema at age 4 (P = .002). In contrast, children who lived with cats before age 1 and were SPT-positive to cat at ages 1, 2, and 3 years were 13 times more likely to have eczema at age 4 than those who were SPT-negative to cat (P < .001).
A history of parental eczema, SPT positivity to egg at 1 year of age, and SPT positivity to elm tree pollen at ages 1, 2, or 3 years were all found to significantly increase the risk of development of eczema at age 4 years. Dog ownership before 1 year of age significantly reduced the risk of eczema at age 4 years among children sensitized to dog. In contrast, cat ownership before 1 year of age significantly increased the risk of eczema at age 4 among cat-sensitized children.
The prospective design of the study is a strength; however, recall bias and the relatively small total number of children with eczema and either cat or dog ownership are limitations. The protective influence of dog ownership on the development of eczema has been reported previously and deserves further investigation into the exact effects of dog antigens on the immune system. Conflicting data regarding the effects of cat ownership on the development of atopy have been reported in other study reports, and larger studies need to be performed before advice regarding pet ownership is given to parents on a routine clinical basis.
- Copyright © 2011 by the American Academy of Pediatrics