Daily doses of peanuts could desensitise adults with the allergy

Adults with peanut allergy reduced their risk of reactions by eating a little peanut protein every day as part of a trial. This approach is already approved in the US for children with the condition.

Peanut allergy occurs when the immune system mistakenly identifies proteins in the legume as a threat. It responds by producing more IgE antibodies, which are a vital part of the immune response, but go into overdrive with allergic reactions. As a result, inflammation ramps up, causing symptoms such as swelling, itching and vomiting. In extreme cases, it can lead to anaphylactic shock, a life-threatening reaction that can affect someone’s breathing or their heart rate.

Until recently, the only solution was to avoid peanuts, but an intervention called oral immunotherapy was approved for children with the allergy in the US in 2020. This involves training the immune system to tolerate the allergen by exposing it to gradually increasing doses of peanut proteins.

However, it was unclear if the approach also worked in adults. “Most of the life of a peanut allergic individual is spent as an adult, but we’ve had no treatment to reduce their underlying reactivity to peanuts,” says Stephen Till at King’s College London. “There are some grounds for suspecting that adults would be more hard to desensitise than children because your immune system is easier to modify when you’re younger.”

To fill this knowledge gap, Till and his colleagues recruited 21 adults with peanut allergy. At the start of the study, the participants were only able to eat up to an eighth of a peanut, on average, before having an allergic reaction.

The team had each participant eat the protein equivalent of one 40th of a peanut every day for two weeks. This dose was slightly increased every two weeks for several months, until they could safely and consistently eat the protein equivalent of four large peanuts every day for a month.

Three participants dropped out of the study due to allergic reactions, while three others left due to reasons unrelated to the treatment. “This dropout number is acceptable for this kind of treatment,” says Cezmi Akdis at the Swiss Institute of Allergy and Asthma Research.

The remaining 15 participants took part in an allergy test where they ate increasing doses of peanut protein under the researchers’ supervision. All but one of them was able to eat the equivalent of five peanuts without having an allergic reaction.

In another part of the experiment, the team analysed blood samples collected from the participants before and after they received oral immunotherapy. This revealed that the intervention caused them to have higher levels of IgG antibodies, which counteract the effects of IgE antibodies.

“It is very promising,” says Akdis. “This approach could mean that adults with peanut allergy can be relieved of the anxiety of eating food contaminated with peanuts.”

But this was a relatively early-stage trial, and larger ones are needed to verify the results and establish how long the protection lasts, he says. “I’d expect you’ll need to take daily or regular doses of peanuts in the long term to maintain the tolerance to the allergen,” says Akdis. “People take pills every day, so I think people affected by peanut allergies may well be fine adhering to this sort of method.”

You should never try to treat allergies without medical supervision.