Scientific Method / Science & Exploration

Six-month treatment limits problems with peanut allergies

Gradual exposure leads to "clinically meaningful increase in peanut threshold."

Food allergies present a significant challenge for many people since items that trigger severe reactions may show up in processed foods without anyone's knowledge. Ingesting too much of an allergen can set off anaphylactic shock or cause a swelling of the throat that makes breathing difficult.

Peanut allergies are among the more prevalent food allergies and may affect over one percent of the children in developed countries; exposure to peanuts has been fatal for some of these individuals. So finding a way to build up a tolerance to peanuts can significantly improve a child's quality of life—as well as that of his or her parents. But there may be some hope on the horizon. A pilot study suggests that a very carefully controlled exposure to peanut-containing food can help build tolerance in those with allergies.

It's important to note that this is a very preliminary study involving fewer than 100 children. The process of exposing allergic individuals to peanuts was carefully controlled, and, even then, a number of the participants had severe reactions. These included wheezing, and, in one case, a participant gave himself an adrenaline injection. Perhaps most significantly, it didn't work for everyone. So if it wasn't already obvious: don't try this at home.

That out of the way, how did this work? Normally, people with peanut allergies are told to avoid anything with even a hint of peanuts in it. But we've known for some time that the immune system can develop tolerance for things it would normally react to—provided it's exposed to them for extended periods of time. But so far, attempts to inject people with peanut-based material haven't led to a development of tolerance.

Reasoning that it might be better to expose people to the allergen in the same way that they'd normally get it—through oral ingestion—the researchers developed a routine where children were given small doses of peanut-based food in a very controlled manner. Over the course of six months, the children were given doses of 2, 5, 12.5, 25, 50, 100, 200, 400, and 800mg of peanut protein. The first time at a new dose was performed in a clinical setting; if that was tolerated, their parents simply incorporated it in their regular meals.

In the first round of the study, half the children were given this treatment, the other half a placebo. By the end of the round, 84 percent of the people in the experimental group were able to tolerate the 800mg dose of peanut proteins. Over half were able to tolerate 1,400mg of peanut—roughly equivalent to eating 10 of them. In a second round, the authors gave the controls the chance to receive the treatment; 91 percent ended up tolerating the 800mg dose, and the majority was again able to tolerate even higher doses.

Again, the procedure wasn't pleasant for them; a lot of people ended up with nausea and vomiting, while others had itchy mouths or suffered from throat constrictions. And to maintain their tolerance, the children have to continue ingesting the 800mg dose for at least three more months, probably more.

But the benefits are substantial. Accidental ingestion of a small amount of peanut changed from potentially life threatening to a non-event. It greatly reduces the risk of day-to-day life, and most participants rated the treatment as improving the quality of their lives.

The Lancet, 2014. DOI: S0140-6736(13)62301-6  (About DOIs).

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