SAN DIEGO – Waiting 3 months after successful oral immunotherapy for peanut allergy before exposure to peanuts significantly increased the odds of reactivity returning in a prospective study of 20 children.
All 20 patients became desensitized to peanuts while on daily oral immunotherapy and successfully passed double-blind, placebo-controlled food challenges at the end of immunotherapy. All 16 patients who then avoided peanuts for 1 month passed a second food challenge, but only 1 of 4 patients who avoided peanuts for 3 months after immunotherapy passed a second one.
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Patients who wait 3 months to be exposed to peanuts after successful oral immunotherapy for a peanut allergy actually increase the odds of reactivity, a recent study found.
"If you wait long enough, the desensitization effect may well wear off," Dr. Brian P. Vickery said at the annual meeting of the American Academy of Allergy, Asthma, and Immunology.
He and his associates looked at levels of basophil activation and conducted skin prick tests to peanut to get a better sense of why this was happening. Basophil activation to peanut antigen and anti-IgE stimulation increased significantly between the times of the first and second food challenges in the patients who avoided peanuts for 3 months but not in those who avoided the nuts for only 1 month.
The basophil activation levels had been similar between groups at the end of immunotherapy, suggesting that desensitization succeeded in all patients, but the length of peanut avoidance affected basophil responses, leading to revival of clinical reactivity.
Skin prick test results returned to baseline levels in three of the four patients who avoided peanuts for 3 months after the end of immunotherapy.
The amount of time on oral immunotherapy did not seem to be a key factor in the likelihood of sustained suppression of allergic disease, reported Dr. Vickery of the department of pediatrics at the University of North Carolina at Chapel Hill. Patients who waited 1 month before exposure to peanut had been on approximately 20-50 months of oral immunotherapy, and patients who waited 3 months before exposure had been on approximately 60 months of immunotherapy.
The lead author of the study was Michael D. Kulis Jr., Ph.D., also of the university.
Prolonged avoidance of peanut after peanut oral immunotherapy appears to be detrimental and may reverse the effects of the treatment, Dr. A. Wesley Burks said at a press briefing.
The findings may be applicable to other food allergies, but "we don’t know that because there have not been enough studies that long with other foods," said Dr. Burks, a coinvestigator in the study and chairman of the department of pediatrics at the university. "I wouldn’t anticipate that it would be different."
The average age of children in the study was 6 years.
This exploratory study was not controlled and was limited by its small size. The Peanut Oral Immunotherapy in Children (IMPACT) study is underway and should answer the question of how long the clinical effects of oral immunotherapy last, Dr. Vickery said. The study is being sponsored by the Immune Tolerance Network and the National Institute of Allergy and Infectious Diseases.
Dr. Vickery, Dr. Kulis, and Dr. Burks reported having no financial disclosures. The National Institutes of Health funded the study.
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