Allergen immunotherapy aims to desensitize a person to a given allergen, which is to say, to raise the person’s reaction threshold to this allergen. The ideal is to reach sustained unresponsiveness — a lack of adverse reactions to an allergen after immunotherapy has been discontinued for some time.

A 2017 meta-analysis of 31 trials looking at the effects of allergen immunotherapies (mostly OIT) on IgE-mediated food allergies reported a substantial benefit in terms of desensitization (risk ratio: 0.16) and sustained unresponsiveness (risk ratio: 0.29), though the latter finding was based on a small number of studies.^[1]

When it comes to treating IgE-mediated food allergies, there are three immunotherapy options: oral (OIT), sublingual (SLIT), and epicutaneous (EPIT).

Oral immunotherapy

For sublingual immunotherapy, the overall scheme is similar, but the doses are typically much lower and the build-up phase is typically much faster.

Of those three options, OIT has yielded the best clinical and immunological outcomes: most people get desensitized to the problem food, and some achieve sustained unresponsiveness for weeks to months. For instance, one randomized controlled trial found that, of 40 children receiving egg OIT, 55% achieved desensitization at 10 months and 75% at 22 months.^[2] Furthermore, of the 30 children who achieved desensitization, 28% exhibited sustained unresponsiveness 8 weeks later.

But if the results of OIT are impressive, so are the risks. Gastrointestinal issues affected 20% of the participants, and more importantly, serious allergic reactions were relatively frequent: a few studies with small sample sizes reported a handful of severe reactions, and one larger study in 395 children reported that 95 of the 240,351 doses caused a severe reaction requiring epinephrine administration.^[3]

SLIT and EPIT have less impressive results than OIT does, but they are safer.

SLIT involves the daily application of an allergen under the tongue. After 2–3 minutes, the allergen is swallowed. SLIT offers modest desensitization with little risk of systemic side effects. It has been shown to be inferior to OIT for the treatment of allergies to peanuts and cow’s milk.^[4]^[5] With regard to safety, >98% of the doses used in one relatively large trial didn’t adversely affect the body beyond the oropharynx, and no epinephrine was required to treat the symptoms.^[6]

EPIT involves the application of a small allergen patch (changed every 24 hours) to the back or upper arm. Limited evidence suggests that EPIT is very safe, with mild skin irritation as the only common adverse effect. EPIT’s desensitization effects, unfortunately, are much inferior to SLIT’s, let alone OIT’s.

Egg Allergy

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