UPDATED May 25, 2023 // Editor's note: This story has been updated to address issues regarding confidentiality of a source.
Could an allergy be the real culprit behind gastrointestinal symptoms similar to irritable bowel syndrome (IBS)? For at least some patients, the surprising answer is: Yes.
That’s the conclusion of New York gastroenterologist Yevgenia Pashinsky, MD, who is spreading the word that a little-known condition called systemic nickel allergy syndrome (SNAS) can mimic some of the symptoms of IBS.
Pashinsky, a partner with New York Gastroenterology Associates and assistant professor of medicine at Mount Sinai School of Medicine, presented her findings and case studies as part of a seminar on SNAS and IBS "mimickers" at the Food and Nutrition Conference and Expo in Orlando last October, sponsored by the Academy of Nutrition and Dietetics.
She and two registered dietitians in her practice, Suzie Finkel, MS, RD, CDN, and Tamara Duker Freuman, MS, RD, CDN, told seminar attendees that SNAS is rarely diagnosed and can be mistaken for IBS. They noted that it probably strikes more people than doctors suspect.
"Systemic nickel allergy is present in at least 10% of the US population (and much higher in some subgroups)," Pashinsky told Medscape Medical News. "But its connection to GI symptoms and functional GI disorders is still being learned about.”
"I think of nickel allergy and other allergic disorders when, in addition to GI symptoms, the patient reports skin and mucous membrane involvement along with their abdominal reactions," she added.
For patients with SNAS, the diagnosis and treatment of this condition are simple and effective.
When patients have nontraditional IBS food triggers, that’s a clue they might have SNAS, Finkel told Medscape Medical News.
"So, that's a situation where, as dietitians we say, 'Hmm, that's weird; if you have IBS, then peanuts and shrimp shouldn't really cause an issue here.' But this might be something physicians might not be attuned to because it's not part of their training," she said.
Finkel said patients with such symptoms are typically referred to an allergist to test for skin sensitization to nickel. If they test positive, they are placed on a low-nickel diet, which has been shown to improve symptoms.
"Doctors who treat IBS patients [who are not responding to treatment] need to consider the possibility that they have SNAS and send them for allergy testing," Finkel said. "If they come back positive, simple dietary changes can address it."
An Underrecognized Condition
There has been very little research regarding SNAS, and there are no standard guidelines for diagnosing and treating it.
What's more, many gastroenterologists aren't familiar with it. More than a dozen gastroenterologists who were contacted for comment declined to be interviewed because they didn't know about SNAS — or enough about it to provide useful information for the story.
Finkel said she's not surprised that many gastroenterologists don't know much about how SNAS can mimic IBS, which is why she and her colleagues presented the seminar last October in Orlando. "It's really an allergy and not a GI disease. It manifests with GI symptoms, but the root is not in the digestive tract; the root is in a true allergy — a clinical allergy — to nickel."
Complicating the issue is that people who have IBS and SNAS typically share some common symptoms.
Like IBS, SNAS can cause GI symptoms — such as cramping, abdominal pain, heartburn, constipation, gaseous distension, and mucus in the stool. It can be triggered by certain fresh, cooked, and canned foods.
But the food triggers that cause SNAS are not usually those that cause IBS symptoms. Rather, SNAS flare-ups are nearly always triggered by foods with high levels of nickel. Examples include apricots, artichokes, asparagus, beans, cauliflower, chickpeas, cocoa/chocolate, figs, lentils, licorice, oats, onions, peas, peanuts, potatoes, spinach, tomatoes, and tea.
According to the American Academy of Allergy Asthma and Immunology, a distinguishing feature of SNAS is that it can cause allergic contact dermatitis when a person touches something made with nickel. Coins, jewelry, eyeglasses, home fixtures, keys, zippers, dental devices, and even stainless-steel cookware can contain allergy-triggering nickel.
What Finkel sees the most are skin reactions from touching a surface containing nickel or from ingesting it, she said.
The other immediate symptom is abdominal pain or changes in bowel movements, such as diarrhea, she added.
Christopher Randolph, MD, an allergist based in Connecticut, told Medscape Medical News that it's important for doctors to realize that patients who have a skin reaction to nickel may also have inflammatory GI symptoms.
"We definitely need more controlled studies," said Randolph, a clinical professor of allergy and immunology at Yale University. "But the takeaway here is for patients and certainly providers to be mindful that you can have systemic reactions to nickel, even though you implicate only the contact dermatitis."
Diagnosis and Treatment Recommendations
Skin-patch allergy testing — in which a person's skin is exposed to nickel — can quickly determine whether a patient with IBS is actually experiencing inflammatory reactions to dietary nickel and would benefit from a low-nickel or no-nickel diet, research shows.
For these patients, Pashinsky recommends the following:
Limiting canned foods
Using nonstainless cookware, especially for acidic foods
Boiling foods for potential nickel reduction, especially grains and vegetables
Running the tap before using water to drink or cook with first thing in the morning
Pashisky and her team also recommend the following guidelines for doctors:
Ask patients if symptoms occur immediately after eating certain high-nickel foods or worsen with a low-FODMAP diet.
Determine whether a patient is not responding to typical medical and dietary interventions used to treat IBS.
Conduct a food/symptom history to identify potential nickel allergy triggers.
Try a low-nickel dietary intervention to see whether a patient's symptoms improve in a week or two.
Refer the patient for additional diagnostic skin-patch testing or treatment.
A Multidisciplinary Approach
Finkel said it's important for doctors, particularly gastroenterologists, who treat patients for suspected GI disorders to consider nickel allergy as a cause.
"SNAS is this overlooked condition...and the research is really in its nascency here," Finkel said.
"I would say only give [a low- or no-nickel diet] consideration if the high-nickel foods are a possible trigger," she said. "It is very specific, looking at their diet history, to have a clear hypothesis based on what their triggers are. It's not something to try out lightly because it's a very restrictive diet, so I would never put a patient on a diet that I didn't think was necessary."
Finkel added that SNAS requires a multidisciplinary approach to treatment — a gastroenterologist, an allergist, and a dietitian.
Doctors and dieticians have distinct roles in identifying and treating these patients, Finkel said.
"If there is a suspicion of IBS symptoms and the patient is not responding to first-line treatments, then it is worth having the input of a dietitian and an allergist," she said.
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Cite this: Are You Misdiagnosing IBS? Watch Out for This Mimic - Medscape - Mar 10, 2023.