SAN DIEGO – About 90% of patients reported improvement in symptoms of irritable bowel syndrome after avoiding type 4 food allergens identified by skin patch testing, according to an uncontrolled study.

Furthermore, 69% of patients reported at least moderate improvement after eliminating foods to which they reacted, said Dr. Michael Stierstorfer, a dermatologist at East Penn Dermatology in North Wales, Pa., who partnered with gastroenterologists at Temple University to conduct the study. “This raises questions about a possible overlap between IBS and allergic contact enteritis,” the researchers stated in a poster presented at the annual Digestive Disease Week.

Dr. Michael Stierstorfer and Dr. Grace Shin

Irritable bowel syndrome is often treatment refractory and tends to elude conventional diagnostics. That was the case for Dr. Stierstorfer, who several years ago developed symptoms of IBS with constipation (IBS-C) that eventually affected him about half the time, he said in an interview. A hydrogen breath test, upper endoscopy, colonoscopy, abdominal/pelvic CT, and tests for gluten-sensitive enteropathy and parasites revealed no abnormalities except decreased small intestinal motility, he said.

But after “flaring badly” twice when he ate Indian food, he began to suspect a cause. “I stopped eating garlic and within a day, I was absolutely fine,” Dr. Stierstorfer said. “The symptoms recurred only if I accidentally ate garlic again.”

Studies had refuted links between IBS and type 1 hypersensitivity but had not explored the role of type 4 (delayed) hypersensitivity in the disorder, Dr. Stierstorfer discovered. “Dermatologists do patch testing all the time for patients with refractory eczema to search for type 4 allergic contact factors that might be causing their rash,” he said. “I performed a patch test of garlic on myself to look for a type 4 allergy, and it was strongly positive. I thought I probably wasn’t the only person walking around with symptoms that mimicked IBS but were really from a type 4 food allergy.”

He tested that idea by skin patch testing 50 patients with IBS symptoms whom he recruited through his dermatology practice. In all, 30 (60%) patients reacted to at least one food allergen, of whom 14 (46%) reported symptomatic improvement after eliminating the suspected triggers from their diets. The findings appeared in the March 2013 Journal of the American Academy of Dermatology (68:377-84).

Next, Dr. Stierstorfer partnered with Dr. Grace Shin, a 3rd-year gastroenterology fellow at Temple University, Philadelphia, and her colleagues. Together, they tested 57 patients with physician-diagnosed IBS with diarrhea (about 43% of patients), IBS with constipation (16%), mixed IBS (30%), or unsubtyped IBS (11%). Patients averaged 41 years of age (standard deviation, 15 years) and 77% were female. Each patient had between 118 and 122 individual allergen patches placed on his or her back. Two days later, the patches were removed and the skin evaluated for macular erythema consistent with a type 4 hypersensitivity reaction. The patients were checked again a day or 2 later to catch any highly delayed reactions.

In all, 56 patients (98%) showed evidence of at least one hypersensitivity, and most reacted to between two and three allergens, Dr. Stierstorfer said. The most commonly identified triggers were cinnamon bark (35 patients; 61%) and sodium bisulfite (26 patients; 46%). At baseline, patients rated their abdominal pain or discomfort at an average of 6.7 on a 10-point severity scale (SD, 2.3 points). After 2-4 weeks of avoiding allergens to which they developed macular edema, they reported a mean 4.4-point improvement in their abdominal symptoms (SD, 2.7 points; P less than .001).

The patients also reported an average 5.8-point improvement on a 10-point scale of global IBS symptom severity (SD, 3.2 points; P less than .001). Overall, 91% of patients reported at least partial relief of abdominal symptoms, while 89% of patients reported at least partial relief of global symptoms, the investigators reported.

Based on these results, “food-related type 4 hypersensitivity reactions may contribute to the pathogenesis of IBS and IBS-like symptoms,” Dr. Shin said in an interview. “The idea of allergic contact enteritis intrigued me, because it made me think that some patients diagnosed with IBS, especially IBS with diarrhea, might benefit from allergy testing when the standard approaches don’t work.”

Another dietary intervention for IBS, the low-FODMAP diet, can help relieve symptoms, “but it’s a hard diet to follow,” Dr. Shin added. “Being able to focus on eliminating one or two things would be easier than eliminating multiple classes of foods that are so common to an American diet.”

Next, the team is planning a controlled trial of the skin patch test. “There is still more validation work to do,” said Dr. Stierstorfer. “But I think this shows that looking at something from a unique perspective – in this case, a dermatologic perspective for a GI problem – can result in a new approach, and potentially an advance in medicine.”

Dr. Shin had no disclosures. Dr. Stierstorfer disclosed financial ties to IBS Centers for Advanced Food Allergy Testing.

Skin patch testing pinpoints dietary triggers of IBS