Immunotherapy for peanut allergies is still a work in progress

Dear Dr. Roach: Why aren’t people able to see an allergist to be desensitized to a peanut allergy? As a child, I was allergic to dust, pet hair, milk and other things, but I received treatments. I am not bothered by any of these now. It would seem prudent to desensitize people who have allergies that are lifethreatening, like peanut allergies.

S.S.

Answer: Allergy immunotherapy continues to be a commonly used and valid treatment for many allergies, including environmental allergies, insect venom allergies, and more recently food allergies. The treatment can be used for peanut allergies, but it is certainly not perfect. So, it isn’t used very often.

The goal of immunotherapy is to get a person to tolerate the allergen that they have an allergic response to. This involves giving very tiny amounts of the allergen below the level that would trigger an allergic response. Over time and under extremely close observation, the amount of the allergen is increased. For allergens like pollen, they are typically given by injection under the skin (or by drops under the tongue), but for food allergens, they are given orally.

For peanut allergies in particular, reactions are common during oral immunotherapy. For about 1 dose per 1,000 under supervision in an allergist’s office, emergency treatment with epinephrine was required. Even during maintenance therapy at home, a reaction occurred 3.5% of the time, requiring treatment in 0.7% of all doses.

Although oral immunotherapy is effective at getting people to tolerate peanuts, the effectiveness is not long-lived, with only 13% still able to tolerate a peanut challenge three years after discontinuing maintenance therapy. (Thirty seven percent of people who continued maintenance therapy were able to tolerate the peanut challenge.)

Until there are significant improvements in outcomes, I am unlikely to recommend oral immunotherapy for people with peanut allergies, unless they are unable to effectively avoid exposure to peanuts and continue to have repeated reactions. Whether they’re on immunotherapy or not, patients are still advised to continue careful avoidance and have emergency treatment immediately available.

A new treatment for food allergies was just approved by the Food and Drug Adminstration. Omalizumab works by blocking the immunoglobulin IgE, which is critically important in allergic diseases. The study showed that 47% to 80% of subjects who were treated with omalizumab (given by injection every two to four weeks) for four months were able to tolerate a standard dose of the foods that they were allergic to (peanuts, plus at least two other foods). However, it appears that the benefit of the treatment does not persist after the treatment is discontinued, and it is intended for use in conjunction with food allergen avoidance to protect against accidental exposures.

In the future, combining this new medication with oral immunotherapy could be superior to using either alone, and it can help prevent serious or fatal allergic reactions from inadvertently being exposed to peanuts. Further studies are addressing this issue.