PURPOSE OF THE STUDY.
To determine the prevalence of food sensitization and clinical food allergy among siblings of food-allergic children.
Children were enrolled as part of the Chicago Family Cohort Food Allergy study. Eligible families had 1 index child with confirmed food allergy and at least 1 sibling participating in the study. There were 478 food-allergic children and 642 siblings. Of index children, 63.6% were male, and 50% were between the ages of 2 and 5 years. Of siblings, 66.5% were younger than the index child.
A structured questionnaire-based interview was performed with each parent. Serum IgE (sIgE) values for 9 common food allergens (egg white, sesame, peanut, soy, cow milk, shrimp, walnut, codfish, and wheat) were measured for each subject. sIgE values ≥0.35 KU/L were considered positive. Serum prick tests (SPT) were performed for the same food allergens, with fish mix and shellfish mix used instead of codfish and shrimp. A mean wheal diameter 3 mm greater than the saline control was considered positive. Oral food challenges were not performed. Stringent clinical criteria indicative of highly likely clinical food allergy were met if a subject had evidence of sensitization and a reported history of symptoms of an allergic reaction to a food within 2 hours of ingestion.
Among siblings of food-allergic children, 13.6% had clinical food allergy, most commonly to milk (5.9%), followed by egg (4.4%) and peanut (3.7%). The prevalence of sensitization to any food without clinical allergy was 53%, while 33.4% of participants had neither sensitization nor clinical allergy. The most common sensitizing foods were wheat (36.5%), followed by milk (35.4%) and egg (35.1%). Risk factors associated with the development of clinical food allergy in siblings included a history of asthma (RRR 4.14; 95% CI, 2.04–8.59; P < .01) and eczema (RRR 3.60; 95% CI, 2.04–6.34; P < .01). Furthermore, eczema was significantly associated with sensitization (RRR 1.66; 95% CI, 1.12–2.45, P < .05)
Although 13.6% of siblings of food-allergic children had a clinically reactive food allergy, the majority (53%) were sensitized to food but did not have clinical food allergy.
Parents of food-allergic children are often concerned about the presence of food allergy in the children’s siblings and seek testing. This study demonstrated that the risk of clinical food allergy is only slightly higher in siblings of food-allergic children (1 in 8) compared with the general population (1 in 12). On the other hand, the rate of asymptomatic sensitization without clinical food allergy is high. Therefore, screening siblings for food allergy is likely to result in a high rate of misdiagnosis and unnecessary dietary restriction, potentially leading to adverse outcomes. These findings are in agreement with the NIAID food allergy guidelines, which do not recommend screening siblings of food-allergic children. In specific situations, such as in the case of parents who express marked anxiety about introducing allergenic foods to the siblings, skin testing and/or sIgE testing for foods may be performed with the understanding that an oral food challenge may be needed to confirm clinical allergy when sensitization is demonstrated.
- Copyright © 2017 by the American Academy of Pediatrics