The GutFit Nutrition Podcast · Leigh Merotto, Dietitian | IBS, Gut Health and Fitness Expert

36: Runny Nose, Fatigue, Bloat, Rashes? Unpacking Histamine Intolerance & the IBS Link

·59 min·6 clips

Leigh Murado opens by linking higher histamine in the gut to the research conversation around IBS. She treats histamine intolerance as a breakdown problem, not just a question of exposure. The main mechanism she describes is DAO deficiency. DAO, or diamine oxidase, is the enzyme that helps clear histamine. When that system is not working well, histamine can build up and symptoms can slowly creep in. She compares the pattern to the immune system behaving as if something harmful is happening, even when the trigger is not a classic allergy. The conversation uses celiac disease and peanut allergy as rough reference points, while making clear that the conditions are not the same. That comparison makes the immune logic easier to follow without flattening the differences. She also points out that histamine-related reactions often seem delayed instead of immediate. That timing can make the condition harder to spot, because the body can appear fine until the bucket gets too full. The episode spends time on mast cell activation syndrome as part of the wider symptom picture, but it does not merge the two conditions into one. Leigh stays careful about where the evidence is still thin. She answers a question about COVID vaccines and immune disorders by saying she has not seen literature that lets her draw a conclusion either way. She also avoids saying that unmanaged histamine intolerance definitely turns into mast cell activation syndrome. Instead, she explains that she does not have enough confidence to say that yet and that the underlying mechanisms do not seem clearly linked. That restraint keeps the episode from overselling a theory. The tone stays practical and listener-facing throughout. It keeps returning to what the symptoms might mean, how they can build, and why a person might need a more careful clinical conversation. The closing section shifts into listener support and community prompts, reinforcing that the show is meant to help people make sense of persistent gut symptoms and the broader factors around them.

As heard by us

A careful look at DAO deficiency, histamine buildup, and the uncertain line between histamine intolerance and mast cell activation syndrome.

The piece frames histamine intolerance as a practical, grounded idea: DAO deficiency may leave histamine less well broken down, and that excess may fit into the IBS picture.

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Why you'd press play

If your gut symptoms may involve histamine buildup, this gives the puzzle some shape.

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