Food Allergies Tied to Irritable Bowel Syndrome?

Medically Reviewed by Arefa Cassoobhoy, MD, MPH on November 12, 2015

Nov. 12, 2015 -- Food allergies and genes that raise your odds of getting allergic diseases might play roles in some people's irritable bowel syndrome (IBS), two new studies suggest.

Allergic asthma, rhinitis, and eczema go hand-in-hand with diarrhea and bad digestive reactions to food in certain people with IBS, researchers say.

"The thinking is that if you can figure out their food allergies, you can really improve their diarrhea and abdominal pain. And we see in the clinic that they do feel better," says senior researcher Mary Tobin, MD, an allergist at the Rush University Medical Center in Chicago.

The findings of both studies were presented at the American College of Allergy, Asthma, & Immunology 2015 Annual Scientific Meeting.

In one study, Tobin and her colleagues spotted a possible connection between allergic rhinitis, asthma, and the allergic gut.

They evaluated 122 with people with IBS tied to allergies and 32 with IBS and no allergies. Those with IBS associated with allergies were more likely to have diarrhea as their main problem. And those with IBS and no allergies were more likely to have constipation as their main symptom.

The diarrhea is possibly from reactions that are similar to what happens with food allergies, Tobin says.

Testing for Food Allergies

In the second study, 48 people who had IBS with diarrhea -- 65% of whom reported having digestion problems after eating specific foods -- got a test to see if their skin reacted to food allergens including peanuts, tree nuts, fish, shellfish, egg, milk, cereals, meats, poultry, fruits, vegetables, and legumes.

The tests showed that 60% of the people's bodies were primed to react to their suspected trigger food. Of those people, 17% also had responses to their trigger food, such as hives, swelling, abrupt nausea and vomiting, and asthma.

These findings indicate that food allergies have a significant role in IBS with diarrhea, says Tobin, who was also involved in this study.

Second Opinion

There are "several points of weakness" in this research, says Antonio Carroccio, MD, of Ospedale Civili Riuniti in Italy.

The link between IBS and having genes that raise your risk of getting certain allergies is "well known and real," and there is "a probable” role food allergies play in IBS-like symptoms, he says. But the study is limited to skin-prick testing, which can't show for sure that a person is allergic, he says. 

Carroccio, who was involved in a recent review of food allergies and IBS, says he tends to agree that "food allergy could be a possible cause of irritable bowel syndrome,” and doctors should work on easing their patients’ symptoms through diet changes. But the work by Tobin's team and others "has yet to prove this," he says.

In the study that used the skin-prick test, "no direct relation can be proved between the foods and the IBS,” he says.

These findings were presented at a medical conference. They should be considered preliminary as they have not yet undergone the "peer review" process, in which outside experts scrutinize the data prior to publication in a medical journal.

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American College of Allergy, Asthma & Immunology (ACAAI) 2015 Annual Scientific Meeting, Nov. 5-9, 2015, San Antonio.

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