After analyzing health insurance data from more than 8 million people in Austria, researchers found that prescriptions of anti-allergy medications were surged in those who were prescribed stomach acid inhibitors, and a class of drugs that included proton-pump inhibitors and H2 blockers.
The findings, published Tuesday in the medical journal Nature Communications, suggest that disruption of the stomach's delicate balance of acids and enzymes may cause our immune systems to go haywire, triggering allergies that did not previously exist.
"We need it has a general awareness that the stomach has an important digestive function, and it has a kind of sterilizing function, "said Dr. Erika Jensen-Jarolim, study lead author and professor at the Medical University of Vienna.
"What we get in terms of food and bacteria is actually denatured and degraded in normal stomach function," she told CNN. "When you take anti-acids, this function is impaired, and we have a wide-open window, and many things enter the intestines that are not good."
It's not completely understood how medications contribute to allergies, but one explanation may be that reduced stomach acid allows undigested food to sneak out of our stomachs.
"Food allergens are large proteins, they're part of large complexes, and we know that when anything we eat hits the stomach, it gets degraded, "said Dr. Caroline Sokol, a physician and researcher at Massachusetts General Hospital who was not involved in the study.
"If you don't have any acid," she said, "you can imagine you've got these big protein chunks that might get through a leaky gut wall. If you're showing your immune system these whole proteins that it can't usually see, then you're at a higher risk of potentially developing an immune response against them. "
Gastric acid inhibitors may also induce allergic bias in patients toward seasonal troublemakers like grass pollen, Jensen-Jarolim said. "There is evidence that anti-acid drugs don't just act on the digestive system, but they also act on immune cells, causing a release of pro-allergic substances."
'Luxury mice' offered first clues
While "there are still lots to come in the future" to understand the link between acid-targeting drugs and allergies, Jensen-Jarolim says she's studied the connection for years.
She got her first lead about two decades ago: a middle-aged man who said he started wheezing after eating caviar
"It was an interesting case because we, or at least some people, still know exactly when we eat caviar. And our patient knew that he ate caviar for the first time seven years before the (allergic reaction). So, he ate it twice, and he knew that in both instances he was on anti-acid treatment. "
That suggested the man had become sensitized to the caviar the first time he ate it, with too little acid in his stomach to break down the food, Jensen-Jarolim said. "So, that was a model case," she added, "because for other foods, it's not easy to single out the co-factors that occur."
Her the research team then fed both caviar and anti-acid medications to what Jensen-Jarolim jokingly called "luxury mice" and found that they, too, developed allergies. Looking at millions of people, new research has shown the same trend with more common allergens.
"This recent study cannot be neglected by the community," Jensen-Jarolim said. "We have the problem that gastroenterologists will say, well, we prescribe these drugs so much and nothing has happened yet." But allergies can happen years down the line, Jensen-Jarolim said, and "I hope they make the connection now."
'An allergy epidemic'
"We don't know why we have such an allergy epidemic," she said, "but clearly that is happening, and there are probably a lot of reasons why. " Gastric acid inhibitors "could possibly be one of those reasons," she said.
"If you have severe acid reflux, then this is a perfectly fine drug. The risk-benefit analysis is clearly in favor of taking the drugs," Falcon emphasized.
"But we really have to think about the use of chronic medications that people stay on forever," she said, "especially in children where we could really look at promoting food allergies that could stay with them for life."  While those allergies may be uncomfortable and even life-threatening, there are other reasons to consider putting down gastric acid inhibitors. The drugs have been linked to an increased risk of stroke, kidney failure and even early death.
"We all assume that because something is available over the counter, that it does not have risks," Sokol said. "But clearly, every medication that we put into our bodies has risks."