Background. The safety and efficacy of tree-nut oral immunotherapy (OIT) has not been demonstrated to date. Its effectiveness as a treatment paradigm is complicated by the high prevalence of co-allergies to several nuts.
Methods. In a prospective cohort study, 73 walnut-allergic patients, aged 4-20 years, with or without co-allergy to pecan, hazelnut and cashew were studied. The diagnosis of each food allergy was based on a recent immediate reaction or a positive oral food challenge (OFC) together with a positive skin prick test or sIgE. Fifty-five consecutive patients underwent walnut OIT and 18 patients served as observational controls. The rates of pecan, hazelnut and cashew co-desensitization in those desensitized to walnut were examined. The efficacy of a low daily maintenance dose for maintaining walnut desensitization to 4000 mg was tested.
Results. A total of 89% (95% CI 81 – 98%) of patients in the OIT group compared to 0% (95% CI 0 – 17·6%) in the control group were desensitized to walnut. Following walnut desensitization, all pecan-allergic patients (n=46) were desensitized to pecan. In addition, 18/30 (60%) hazelnut or cashew allergic patients and 93.3% for hazelnut alone, were either desensitized or treatment responders (increased reaction dose of ≥10 fold or to a dose ≥1000 mg). Most adverse reactions during up-dosing were mild, but nine patients required intra-muscular epinephrine for home-doses. A low maintenance-dose maintained walnut desensitization. A single patient required epinephrine during maintenance.
Conclusion. Walnut OIT is effective in desensitizing walnut, as well as pecan and hazelnut in co-allergic patients. Adverse events subside with time.
