Peanut allergy is increasing across industrialized countries and is usually lifelong.2,14
The standard treatment for peanut allergy is to follow a strict elimination diet and to treat any reactions from accidental ingestions with epinephrine and antihistamines. However, peanut is difficult to avoid given its ubiquitous presence in the food supply. Therefore OIT offers a promising treatment for peanut allergy. In OIT protocols, the patient is given the allergic food in escalating doses in an attempt to increase tolerance. Because patients are given a food to which they may potentially react, the safety of OIT has been a concern. In this study, we show that a peanut OIT protocol consisting of an initial escalation day, a build-up phase and a home dosing phase is overall safe and well tolerated in patients without a history of severe life-threatening anaphylaxis to peanut ingestion or severe or poorly controlled asthma.
In this study, reactions were most frequently observed during the initial escalation day in which patients underwent an oral desensitization with peanut protein. Twenty-six of 28 patients had symptoms during the desensitization. However, the severity of symptoms varied widely across patients and only 4 of 28 patients received epinephrine for severe symptoms. Six of the 28 patients were able to tolerate the final 50 mg peanut dose of the modified rush desensitization. (see Table E5 in the Online Repository) There was no significant difference in peanut specific IgE levels between those who required epinephrine for severe reactions and those who tolerated the initial escalation day. It is likely that fewer patients would have reactions if the final dose of the initial escalation day was lower thereby extending the duration of the build-up phase.
Doses were better tolerated during the build-up phase than during the initial escalation day. The estimated probability of a reaction with a build-up phase dose was 46%. These reactions were usually mild in nature and there were no severe symptoms recorded during the build-up phase. Moderate symptoms were also less commonly experienced with build-up phase doses than during the initial escalation day. Peanut specific IgE levels were similar between those who had reactions and those who tolerated build-up phase doses
Home doses were rarely associated with any reactions. The estimated risk of a reaction with a home dose was quite low at 3.5%. When symptoms were recorded with home dosings, they were most commonly classified as mild with rare occurrences of more severe symptoms. Although 2 patients were treated with epinephrine for reactions after home dosings, they were both able to reach the maintenance dose of peanut and complete the study.
One interesting finding was the relationship between asthma and chest symptoms during the OIT protocol. Asthma was prevalent in this study population; 68% of the patients were asthmatics. Of those patients who experienced chest symptoms during the initial escalation phase or the build-up phase, 40% and 100% had asthma. Eighty-two percent of the patients who experienced chest symptoms with homes doses were asthmatics. Our experience suggests that having a diagnosis of asthma is associated with a higher rate of chest symptoms during OIT. Only 47% of the asthmatic children were on inhaled corticosteroid therapy during OIT. It is possible that placement of asthmatic children on adequate controller medications with close monitoring of pulmonary function tests prior to and regularly during the OIT study could reduce the incidence of chest symptoms.
OIT has been studied as a treatment for other food allergies. However, OIT for peanut allergy has been described in the literature in only 2 case reports. In a Letter to the Editor, Mansfield describes an oral desensitization protocol using peanut kernels in a peanut allergic child.15
After a rush desensitization followed by an 8 week buildup phase, the child was ingesting 2 whole peanuts twice a day and had tolerated an accidental exposure to peanut without symptoms. This child experienced wheezing and rash during the initial rush desensitization. Patriarca and colleagues report a rush desensitization procedure to peanut followed by a maintenance phase in a peanut allergic woman. Both the desensitization and maintenance phase were well tolerated without any side effects. After 6 months on therapy, skin prick tests which were initially positive were absent and peanut specific IgE had declined slightly. The woman was also able to tolerate peanut containing foods in her diet.16
Given the success of studies of OIT for milk and egg allergies and the rising prevalence of peanut allergy, there seems to be a void of studies related to peanut OIT. This may be due to several interesting features of peanut allergy. Although milk, egg, and peanut allergies are all IgE mediated, there are differences between these food allergies. Peanut allergy has been associated with a high risk of severe anaphylaxis as compared to egg allergy.17, 18
Several studies have found that peanut is the most common cause of fatal food induced anaphylaxis.18–20
Studies have also shown that reactions can occur at very low doses of peanut protein (0.1 mg).14
The paucity of studies on peanut OIT may be related both to the high risk of anaphylaxis with peanut ingestion and the risk of reaction with very low doses of peanut.
In this study of peanut OIT, severe reactions requiring treatment were rare, much different than previous studies of peanut immunotherapy.5
However, we caution that this was a select group of patients treated with peanut OIT in a controlled medical setting by personnel trained in food-induced anaphylaxis. Further studies are needed in larger populations of peanut allergic children to ensure safety of this protocol. Studies are underway to determine the efficacy of peanut OIT and duration of effect. In this study, none of the children had an accidental ingestion of peanut while on the 300 mg of peanut protein. The subjects did have a peanut challenge of 3900 mg at the conclusion of the original period of treatment and 93% tolerated this challenge without symptoms (Jones et al. Manuscript under consideration at JACI). Each of these subjects had allergic symptoms to peanut ingestion of 50 mg or less with the daily dosing early in the study.21
The question remains whether peanut OIT will simply lead to desensitization or to true immune tolerance. If only desensitization is achieved, patients who are being treated with peanut OIT and who have an accidental ingestion will likely be protected from an allergic reaction. However, similar to drug desensitization, if peanut OIT only causes desensitization and is discontinued, the patient would be at risk for reactions if accidental ingestions occur. If immune tolerance is achieved by peanut OIT, then patients may be able to discontinue therapy and reintroduce peanut into their diet without fear of reaction. Even if peanut OIT only results in desensitization and not immune tolerance, it may offer protection for those who may have accidental peanut ingestions. Overall peanut OIT offers a promising therapy with a good safety profile for peanut allergic patients.