The paper, published Thursday in the Lancet
, found that people taking oral immunotherapy -- microdoses of peanut allergen meant to partly desensitize patients over time -- paradoxically had three times the rate of anaphylaxis compared with those taking a placebo. That risk jumped from 7.1% to 22.2%, based on an analysis of more than 1,000 patients across 12 trials. There were no deaths in any of the trials.
Those taking the treatment also reported more epinephrine use and saw roughly double the rate of other kinds of allergic reactions, the study showed. These findings were attributable to the treatment itself, not accidental exposures to foods, according to the authors.
"There have been so many studies coming out about oral immunotherapy for peanut, there's sometimes conflicting information out there about its effectiveness and reliability," said study author and internal medicine physician Dr. Derek Chu, now a final-year fellow in clinical immunology and allergy at McMaster University in Ontario.
Oral immunotherapy has shown promising results
in some trials, but Chu said there may be a disconnect between how researchers measure outcomes in the controlled environment of a research study, versus what happens in the real world.
In clinical trials, researchers often rely on tests like an "exit food challenge," in which patients eat a small amount of peanut under a doctor's supervision. Food allergies, however, are not so predictable. Some patients had allergic reactions to doses of the therapy they'd previously tolerated, the new study says.
"This protection that you get from going through immunotherapy -- that can change every day," Chu said. "If you exercise within two to four hours, or you take a hot shower, or you have an empty stomach, that can all change the way your body interacts with the food that you've supposedly been desensitized to.
"So you can actually have an unpredictable reaction to the thing that's supposed to protect you."
Peanut allergy, along with tree nut allergy, affects an estimated 3 million Americans or more. Experts say its prevalence is on the rise -- and in the majority of cases, it's lifelong.
"We don't have any [approved] treatment for food allergy," said Dr. Alkis Togias, branch chief of allergy, asthma, and airway biology at the US National Institute of Allergy and Infectious Diseases. Togias was not involved in the new paper.
"From our perspective as an agency that is responsible for research in the field, what it tells us is that we need to improve on the methods for treating food allergy, especially peanut allergy," he said.
Hope vs. hype
People with peanut allergies, as well as parents of kids with these allergies, have been holding out for a treatment that can offer some peace of mind. The idea behind oral immunotherapy is not necessarily to eliminate the allergy completely but to reduce the likelihood that accidental contact with peanuts could become serious or deadly.
published in November, for example, found that two-thirds of its young patients were able to eat the equivalent of two peanuts with no severe reaction after a months-long regimen of powder-filled capsules.
In the wake of studies like that one, Chu's analysis may be a wake-up call -- but it doesn't mean all hope is lost. Researchers are already looking for ways around the risks, he said.
"Like the Tesla autopilot, for example, the first generation of any of these things was not perfect," said Chu, who carries an EpiPen for his own peanut allergy.
Togias said there are a number of potential avenues for modifying how we approach oral immunotherapy, including changing the dose and taking it in combination with other medications, such as those that prevent allergic reactions.
"The message is clear: We need to do better," Togias said. "But this is a first step."
Even with additional risks, he added, patients might see a valuable trade-off: Some may want the option of taking such a treatment anyway because they can plan for an allergic reaction at home, while perhaps still offering a layer of security for peanut exposures that happen out-of-the-blue, away from home.
"That's an important piece that is very personal," said Togias.
Experts say that more research is needed in order to improve upon the experimental treatment, look at different ways of delivering the therapy and discover whether there are certain groups of patients who benefit more than others.
"There's hope that we will have something, but we have to separate hope from hype," Chu said. "This is a first crack at a new treatment."