The idea behind immunotherapy for peanut allergy is appealing in its simplicity: Ask a patient to eat tiny amounts of peanut every day, and over time their immune system will become desensitized to it.
Unfortunately, this cure might be doing more harm than the allergy itself, a new evidence review suggests.
People who undergo immunotherapy for their peanut allergies wind up with a large increase in life-threatening anaphylaxis and other allergic reactions, compared to others who either avoid peanuts or are in a placebo group, researchers concluded.
Peanut immunotherapy triples a patient's risk of anaphylaxis and doubles the chances they'll need to use epinephrine to counter a severe allergic reaction.
"We found that patients on immunotherapy, their quality of life wasn't any better," said lead researcher Dr. Derek Chu, a fellow in clinical immunology at McMaster University in Ontario, Canada. "Outside of the clinic, they actually end up having more allergic reactions over time."
Chu's team discovered this troubling fact after pooling results of 12 peanut immunotherapy trials involving more than 1,000 patients.
"If you looked at each study one by one, you might not see that," Chu said. "When you combine them all, and you analyze all 1,000 patients in unison, then you can actually see it."
Food allergies affect more than 6 million people, including as many as 8 percent of children and 3 percent of adults, researchers said in background notes. Although most kids outgrow allergies to milk or eggs, peanut allergies are lifelong in up to 85 percent of cases.
Symptoms can run from runny nose, hives and itching to a tightening of the throat and shortness of breath. Severe reactions can result in anaphylactic shock, which requires immediate treatment with an epinephrine injector and a trip to the emergency room, the Mayo Clinic says.
Right now, immunotherapy is the only available treatment for severe food allergies, and it has been shown to increase a person's tolerance, Chu said.
"There haven't been any other options than avoidance to date, so it's very promising we have something that partially works," he said. But these results show the price paid for increased tolerance might be too high.
"The therapy itself needs to be very carefully reconsidered," Chu said. "That level of protection you get from going through the procedure is variable and often incomplete. Day-to-day, the degree of protection can change, and if you have an infection or an illness or maybe you're just tired that day, you can have a reaction to a dose you previously tolerated."
The 12 clinical trials occurred in the United States, United Kingdom, Europe and Australia. The average age of participants was about 9 years old, and patients were typically followed for a year.
People undergoing peanut immunotherapy had a 22 percent risk of anaphylaxis, compared with 7 percent for untreated peanut allergy sufferers, researchers found.
The chance that a peanut immunotherapy patient would require an epinephrine injection is about 8 percent, compared to about 4 percent for those not receiving treatment. Allergic reactions involving the gastrointestinal tract, skin, nose and lungs also increased.
Researchers concluded that folks might want to simply avoid peanuts rather than undergo immunotherapy if they want to prevent anaphylaxis and allergic reactions.
The new evidence review was published online April 25 in The Lancet.
While these findings are food for thought, it's too early to completely count out immunotherapy, said Dr. Scott Sicherer, director of the Jaffe Food Allergy Institute at the Icahn School of Medicine at Mount Sinai in New York City. He wasn't involved with the study.
"Although this is a very important paper pointing out a major issue with this particular approach, it's not the end of the story," Sicherer said. "It's still a viable approach. It does change the threshold for a majority of patients. But it requires a discussion between the doctor and the patient of the risks and benefits."
Sicherer noted that there is no immunotherapy for food approved by the U.S. Food and Drug Administration. Allergy doctors instead create their own "home brew" for patients, providing either tiny amounts of the food or capsules containing refined versions of the allergen.
That's one problem with current immunotherapy practice, Chu said.
"Anytime we take something that's completely natural, and we distill it and put it in a capsule, that's a drug now," he said. "That's not just something as simple as an off-the-shelf product anymore."
Sicherer's center doesn't offer immunotherapy as a regular clinical option, because the treatment is not FDA-approved, he said. Assuming it ever gets approved, he envisions a conversation where he'd discuss the risks and benefits with a child's caregivers.
"This is a therapy where there's a two-thirds chance it's going to increase the amount of peanut your child can eat before reaction, but going onto this therapy on average results in more anaphylaxis and allergic reactions than if you didn't go on this therapy," Sicherer said.
The therapy would reduce the chances of an accidental allergic reaction caused by traces of peanut winding up in a restaurant meal, but there also could be an out-of-the-blue reaction to the therapy itself, he said.
Chu and Sicherer agreed better treatments are needed. And that might be on the way.
Earlier this month, researchers announced a potential medication for peanut allergy that would halt violent reactions by blocking the immune system's antibodies from responding to the allergen. It was published in the Proceedings of the National Academy of Sciences.
"There's a lot of promise from a lot of different approaches, and I would imagine that we're going to end up in a place, hopefully not too long from now, where we could say, there's seven different options and looking at your situation the best is this one or that one," Sicherer said.
More information Stanford University has more about peanut immunotherapy.
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