LONDON—A British team has identified four factors that can be added to parental history to predict which children are at risk for peanut allergy: soy milk or soy formula intake; a rash over joints and skin creases; an oozing, crusted rash; and use of skin lotions and creams that contain peanut oil.[1] The association between emollient use and peanut allergy was particularly striking—and important, since it suggests a relatively simple way to avoid life-threatening reactions.

“However, our negative findings are almost as important as the positive ones,” said Gideon Lack, MBBCh, a consultant in pediatric allergy at St. Mary’s Hospital in London. Dr. Lack added, “People have increasingly been looking for prenatal risk factors for childhood peanut allergy, particularly maternal peanut consumption in pregnancy, but our study failed to support such an association.”

In a separate study of treatments for peanut allergy, the administration of a monoclonal antibody against immunoglobulin (Ig) E markedly increased the amount of peanut flour necessary to cause an allergic reaction in peanut-sensitive individuals. Among the patients given the highest dose of the monoclonal antibody (450 mg), the tolerance threshold rose from 178 mg of peanut flour (equal to about half a peanut) to 2,805 mg (nearly nine peanuts).[2] The increased tolerance should be enough to protect those with peanut allergy from most accidental exposures, the investigators believe.

NEW RISK FACTORS

Dr. Lack and his colleagues studied 13,971 preschoolers with a maximum age of 38 months. From this group, 49 children with a clear history of peanut allergy were prospectively identified from their parents’ responses. The study also included two sets of randomly selected controls—a subgroup of 140 children who did not have peanut allergy and 70 children from outside the study cohort who had a maternal history of eczema and who had developed eczema within the first six months of life.

In telephone interviews, the parents of all three groups—the children with peanut allergy and both sets of controls—were asked about family history of peanut allergy, maternal peanut consumption during pregnancy and lactation, and whether skin lotions or creams were used on the children. Parents were also asked whether the children had ever suffered from rashes or other skin problems.

Of the 49 children with a history of peanut allergy, 36 underwent skin testing for peanut allergy; the result was positive in 29. Double-blind placebo-controlled food challenges confirmed the allergy in 23 children.

After adjustment for confounding variables, the consumption of soy milk or soy formula had an odds ratio (OR) of 2.6 for peanut allergy; a history of rashes over the joints and skin creases also had an OR of 2.6. In both cases, the 95% confidence intervals (CIs) were roughly 1.3 to 5.0. A history of an oozing, crusted rash had an OR of 5.2 (CI, 2.7 to 10.2). The OR associated with the use of skin lotions and creams containing peanut oil was even higher—6.8 (CI, 1.4 to 32.9).

Once confirmed, these findings may prompt research into strategies to prevent peanut sensitization in at-risk children. Such strategies could include not feeding infants soy products (which may increase risk through cross-sensitization) and protecting children from topical exposure to peanut allergens, Dr. Lack suggested. Avoiding the peanut-containing emollients would be particularly important for children with eczema or other breaks in the skin, he added.

ANTI-IGE THERAPY

The second study, conducted by Donald Y. M. Leung, MD, and colleagues from the National Jewish Medical and Research Center in Denver, was a double-blind dose-ranging trial of TNX-901, a humanized IgG1 monoclonal antibody to IgE. The study included 84 adults and children with a history of immediate peanut hypersensitivity who were randomized to 150, 300, or 450 mg of the study drug or to placebo; treatment was given subcutaneously once every four weeks for four months. Double-blind food challenges with peanut flour were performed at baseline to confirm allergy. Repeat challenges took place two to four weeks after the last treatment was given.

Among the patients who received TNX-901, there was a strong dose-dependent trend toward greater tolerance of peanut challenge; however, the increase in tolerance only reached statistical significance in the 450-mg group. The repeat challenges showed that the proportion of patients who could ingest 8 g of peanut flour (about 24 peanuts) without an allergic reaction was 4% in the placebo recipients, 0% in those administered the 150-mg dose, 21% in those receiving 300 mg, and 24% in those given 450 mg.

Blood studies performed eight weeks after the final treatment demonstrated that TNX-901 administration was associated with large declines in free IgE levels, a finding that confirms the direct role of IgE in peanut hypersensitivity. Rates of systemic adverse events (including diarrhea, nausea, and vomiting) and injection-site reactions (such as erythema and swelling) were similar in the four groups, which suggests that TNX-901 is relatively safe. The drug is still considered experimental, though.

—Timothy Begany