Could You Be Allergic to Avocados?

As a dietitian working in a gastroenterology practice, meeting patients with chronic acid reflux and irritable bowel syndrome is my stock-in-trade. I can recognize the symptom patterns from a mile away, and have developed a sixth sense for what dietary remedies will work for whom.

But over the course of my career, there have been a small handful of patients who arrived at my doorstep with a diagnosis of GERD or IBS but differed from the rest of the pack. On the face of things, their symptoms matched those of everyone else: heartburn, chest tightening, bloating and/or urgent trips to the bathroom triggered by an offending food. But these patients were different.

For starters, they didn’t respond at all to any of the usual dietary remedies. The people with heartburn attacks weren’t provoked by onions, garlic, fatty foods or giant salads – nor did their symptoms respond to the usual acid-suppressing medications. Instead, they were reacting to seemingly random triggers like pumpkin cinnamon scones, cooked spinach and avocado toast.

Similarly, the folks with IBS-like attacks of diarrhea weren’t provoked by the usual culprits like ice cream, fried foods and salads. Instead, they were reacting to leftovers reheated for lunch, tomatoes and soy sauce. And frustratingly, they didn’t get any better from the most effective remedies for IBS like soluble fiber supplements, low-FODMAP diets or prescription medications.

So what looks like IBS and GERD, acts like IBS and GERD, but isn’t IBS or GERD? In these cases, it turned out to be a histamine intolerance.

Histamines are natural signaling chemicals that our bodies produce and use for all sorts of purposes. They play a role in the release of stomach acid and produce the swelling and inflammation essential to our immune system’s ability to heal infections. Of course, when we produce too much histamine – like in response to seasonal allergens – it can provoke unpleasant allergic symptoms like runny noses, sneezing and congestion. (This is why antihistamine medications are used to treat allergy symptoms.) High histamine levels can also cause itching, hives, headaches and asthma-like symptoms.

Some foods like spinach, soy, avocados, pumpkin and tomatoes are naturally high in histamines as well. Other foods develop histamines as a byproduct of aging, fermentation and spoilage. Leftover meat, beer and wine, aged cheese, cured meats, kombucha and yogurt fall into this category.

So what happens if someone – particularly someone whose histamine levels already run high as the result of seasonal or environmental allergies – starts eating lots of high-histamine foods? In come cases, they may experience an inflammatory reaction within the digestive system that produces symptoms very similar to IBS and GERD: chest tightening, heartburn, bloating and/or sudden onset diarrhea. Typically, the symptoms kick in within minutes of eating an offending food. This is called histamine intolerance.

It can be tricky to spot histamine intolerance, because your food reactions may vary based on season – worse in spring and fall; relatively better in winter and summer. You may not react to a small portion of a high-histamine food – leading you to believe it’s safe – or you may react more to certain high-histamine foods than others. If you’ve had traditional allergy testing with blood, it’s likely that none of your trigger foods will have registered as problematic. (But if you’ve had skin prick testing, the histamine control will likely have produced a gigantic wheal!) And unless you know what these seemingly random trigger foods have in common (a high amount of histamine), you’ll be left scratching you head as to why these attacks of digestive distress seem to come on out of nowhere.

But as complicated as identifying histamine intolerance can be, the solution is easy and effective: a low-histamine diet. The basics are below:

  • Avoid foods naturally high in histamine: spinach, avocado, tomatoes (including ketchup and marinara sauce), pumpkin, eggplant, soy foods, brewer’s yeast and kidney (red) beans.
  • Do not eat leftover meats or fish, and freeze fresh meats or fish until you are ready to thaw and cook them.
  • Avoid fermented, cured or cultured foods: wine, beer, aged cheese, smoked fish, salami/prosciutto/pepperoni, kimchi, sauerkraut, kombucha, miso, tofu, soy sauce, yogurt and kefir.
  • Watch out for vinegar-containing foods and condiments, including pickles and olives.
  • Watch out for certain spices: cinnamon, chili powder, cloves, nutmeg and curry powder.
  • Avoid foods that use sulfites as a preservative, like wine, dried fruits, certain frozen potatoes or seafood, shelf-stable lemon and lime juices, and frozen grape juice concentrates.
  • Stay away from foods with artificial colors and chemical preservatives like BHA/BHT.

While there are additional foods (like certain fruits) that may trigger histamine release, the list above is a great place to get started. A registered dietitian who’s familiar with the low-histamine diet can help you home in on a meal and snack repertoire that helps keep your symptoms at bay. A great allergist/immunologist may also be able to devise a histamine-controlling medication regimen that allows you to comfortably expand your dietary repertoire.

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