The results of a Canadian study showed that atopic dermatitis without concomitant allergic sensitization as elicited by skin prick test at age 1 year is not associated with an increased risk for asthma in children reassessed at age 3 years.
The study, published in the Journal of Allergy and Clinical Immunology, considered children sensitized if they produced a wheal 2 mm or larger than that elicited by the negative control to any of the 10 inhalant or food allergens during skin prick testing. Children were also assessed for atopic dermatitis by using the diagnostic criteria of the UK Working Party. At age 3 years, children were assessed for asthma, allergic rhinitis, food allergy, and atopic dermatitis.
Maxwell M. Tran, BHSc, from the Department of Medicine, McMaster University, Hamilton, Ontario, Canada, and colleagues looked at data from 2311 children and found that after adjusting for common confounders, the relative risk (RR) for asthma with atopic dermatitis alone was 0.46. In contrast, children with atopic dermatitis and allergic sensitization had a 7-fold (RR, 7.04) risk for asthma.
Atopic dermatitis and allergic sensitization also had significant interaction on both the additive (relative excess risk due to interaction, 5.06) and multiplicative (ratio of RRs, 5.80) scales in association with asthma risk. Atopic dermatitis and allergic sensitization had a positive additive interaction in their effects on risk of developing food allergy (relative excess risk due to interaction, 15.11) as well.
One potential limitation of the study is that cases of atopic dermatitis classified as definite by clinicians during assessments were likely more severe, whereas infants with milder atopic dermatitis may not have been identified. The authors suggested that future studies should investigate the association between low- to moderate-severity atopic dermatitis and allergic sensitization in relation to the risk for allergic diseases.
The authors also noted that children with atopic dermatitis and evidence of sensitization to common food or inhalant allergens as early as 1 year of age represent a high-risk subgroup. They suggested that this may justify further examination in primary intervention studies.
Tran MM, Lefebvre DL, Dharma C, et al. Predicting the atopic march: results from the Canadian healthy infant longitudinal development study [published online November 15, 2017]. J Allergy Clin Immunol. doi: 10.1016/j.jaci.2017.08.024