Does atopic dermatitis cause food allergy? A systematic review

Background: The association between atopic dermatitis (AD) and food allergy (FA) is not fully understood, although a causal relationship has been suggested. This has important implications for prevention and treatment. Objective: We aimed to review the association between AD and FA, the effect of FA on AD severity, chronicity, and age of onset, and the temporal relationship between the two. Methods: Medline and Embase were systematically searched from inception to November 2014 for studies investigating both AD and FA. Results: Sixty-six studies were identified. Eighteen were population-based, 8 used high-risk cohorts, and the rest comprised patients with either established AD or FA. In population-based studies, the likelihood of food sensitization was up to 6 times higher in patients with AD versus healthy control subjects at 3 months of age (odds ratio, 6.18; 95% CI, 2.94-12.98; P < .001). Other population-based studies reported that up to 53% of subjects with AD were food sensitized, and up to 15% demonstrated signs of FA on challenge. Meanwhile, studies including only patients with established AD have reported food sensitization prevalences up to 66%, with challenge-proven FA prevalences reaching up to 81%. Sixteen studies suggested that FA is associated with a more severe AD phenotype. Six studies indicated that AD of earlier onset or increased persistence is particularly associated with FA. Finally, one study found that AD preceded the development of FA. Conclusions: This systematic review confirms a strong and dose-dependent association between AD, food sensitization, and FA. AD of increased severity and chronicity is particularly associated with FA. There is also evidence that AD precedes the development of food sensitization and allergy, in keeping with a causal relationship.