Eczema, Egg Allergy in Infants May Predict Peanut Allergy

Infants diagnosed with severe eczema or an egg allergy may be more likely to develop peanut allergy (PA), according to baseline results from the Learning Early About Peanut Allergy (LEAP) study.

The study is being conducted to determine whether introducing peanuts in a child's diet early in life or avoiding them altogether is the best strategy for preventing PA. The study is funded by the National Institute of Allergy and Infectious Diseases.

George Du Toit, MBBCh, FRCPCH, a consultant pediatric allergist at King's College London, King's Health Partners, MRC & Asthma UK Centre in Allergic Mechanisms of Asthma, and the Department of Paediatric Allergy, Guy's and St Thomas' NHS Foundation Trust in London, United Kingdom, and colleagues presented early results from the study in an article published online November 21 in the Journal of Allergy and Clinical Immunology.

"This is the first report on the LEAP study, which is a highly anticipated study," Mark Holbreich, MD, an allergist in Indianapolis, Indiana, told Medscape Medical News.

Researchers screened a total of 834 infants 4 to 10 months of age who were suspected of being at risk for developing PA but who had no clinical symptoms. The children were recruited between November 2006 and May 2009 and will be followed up until the age of 5 years. Participants in the randomized portion of the study will be randomly assigned to consume peanut 3 times weekly or avoid it completely from enrollment until the age of 60 months, at which time the prevalence of PA will be determined by oral challenge.

Before randomization, however, the investigators divided the children into 4 groups: group 1, infants with mild eczema and no egg allergy (n = 118); group 2, infants with severe eczema, egg allergy, or both but 0-mm peanut skin prick test (SPT) wheal responses (n = 542); group 3, infants with severe eczema, egg allergy, or both and 1- to 4-mm peanut wheal responses (n = 98); and group 4, infants with greater than 4-mm peanut wheal responses (n = 76).

The investigators will randomly assign the 640 infants from groups 2 and 3 to a peanut or no-peanut diet. Group 1 was excluded because those infants had minimal risk of developing allergy and group 4 was excluded because those infants had a high risk for already having had an allergy.

The current report describes the baseline information for all of the screened infants. The investigators were surprised to learn that 17% of the infants in group 2 had peanut-specific immunoglobulin E (IgE) sensitization (>0.35 kU/L), as did 56% of group 3. None of the infants in group 1 and 91% of those in group 4 had peanut-specific IgE sensitization.

Peanut sensitization on skin testing (SPT response of 1-4 mm vs 0 mm) was associated with egg allergy and severe eczema (odds ratio [OR], 2.31 [95% confidence interval (CI), 1.39 - 3.86] and 2.47 [95% CI, 1.14 - 5.34], respectively). Atopy rose significantly (P < .001) in ascending order from groups 1 to 4 for severe eczema, scoring atopic dermatitis, rates of egg allergy, and eosinophil levels.

"Our data demonstrate that the specific IgE level is a more sensitive indicator of immunologic reactivity than skin test results in infants between 4 and 11 months of age. The most important clinical risk factors for peanut sensitization based on SPT responses and specific IgE levels were egg allergy and severe eczema," the authors write.

The authors also noted that the mean age of children screened also rose in groups 1 through 4, and most of the children in the screening cohort had severe eczema (77%) and egg allergy (57%), as defined by the study.

Study participants who were black had a significantly higher risk for peanut-specific IgE sensitization (OR, 5.30; 95% CI, 2.85 - 9.86), but when specific IgE levels were analyzed, black race had a protective effect against cutaneous sensitization (OR, 0.15; 95% CI, 0.04 - 0.61).

Primary vs Secondary Prevention

"There's a lot of discussion about why there's some discrepancy between the serum assays and the skin test assays in blacks. There appear to be racial differences in food sensitization that are not clearly explained," noted Dr. Holbreich, who was not involved in the study.

"The early sensitization to peanut was surprising because children at a very young age already showed that they were sensitized to peanut. By giving them peanut early in life, in some of the population you may be encouraging primary prevention and in some patients you may be getting secondary prevention by inducing tolerance," Dr. Holbreich explained.

"A number of children who went into this study already were sensitive to peanut, so they're hoping that by introducing them at that stage that they will prevent peanut allergy even though the children are already sensitized," Dr. Holbreich added.

The authors also emphasize this point. "We have identified many infants with large wheals and high specific IgE levels to peanut, which, together with the increasing mean age in groups I to IV, suggests that PA develops rapidly in this age group and that there is a relatively narrow age window of opportunity to intervene and prevent PA," they write.

This study was supported by the Immune Tolerance Network (funded by the National Institute of Allergy and Infectious Diseases), the Food Allergy Initiative, the Food Standards Agency, the Food Allergy and Anaphylaxis Network, the MRC & Asthma UK Centre, and the Department of Health through the National Institute for Health Research comprehensive Biomedical Research Centre award to Guy's & St Thomas' NHS Foundation Trust in partnership with King's College London and King's College Hospital NHS Foundation Trust. The clinical trials unit is supported by the National Peanut Board. Dr. Du Toit and Dr. Holbreich have disclosed no relevant financial relationships. Full conflict-of-interest information is available in the article.

J Allergy Clin Immunol. Published online November 21, 2012. Abstract