Histamine intolerance

Histamine is a signalling molecule the body uses for immune responses, stomach acid production, and brain alertness. Mast cells release it during allergic reactions. It is also present in food, formed when bacteria break down the amino acid histidine during fermentation, ageing, or storage. Aged cheese, cured meats, fermented foods, alcohol (especially wine and beer), and fish that has not been kept cold are typically the highest in dietary histamine.

Two enzymes are proposed to break it down. Diamine oxidase (DAO) is thought to handle histamine in the gut, and histamine-N-methyltransferase (HNMT) handles histamine inside cells. The hypothesis is that if DAO is low or overwhelmed, histamine from food enters the bloodstream and produces symptoms similar to a mild allergic reaction without an immune trigger. Serum DAO levels do not correlate well with symptoms in research settings, so the mechanism remains uncertain even when the symptom picture is real.

• Flushing of the face and chest, often with heat.
• Headache or migraine after trigger foods, especially red wine, often within a few hours.
• Hives, itching, or eczema flares.
• Runny nose, sneezing, watery eyes that look like hayfever but happen indoors.
• Bloating, diarrhoea, or stomach pain after specific foods.
• Faster heartbeat, anxiety, or low blood pressure in more sensitive people.

• Aged cheese (parmesan, cheddar, gouda, blue cheese).
• Cured meats (salami, pepperoni, prosciutto, bacon).
• Fermented foods (sauerkraut, kimchi, soy sauce, miso, kombucha).
• Alcohol, especially red wine, champagne, and beer.
• Fish, especially tuna, mackerel and sardines that have not been kept very cold.
• Histamine liberators (often cited as triggering release rather than being high in histamine): tomato, strawberry, citrus, chocolate, shellfish, food additives.
• Leftovers in general: histamine can build up as food is stored, especially if it is not kept consistently cold.

1. Eliminate high-histamine foods strictly for 4 weeks. Symptoms should noticeably improve in the first 1 to 2 weeks.
2. Reintroduce one category at a time, in small amounts, with at least 3 days between trials.
3. Note your reactions in a log. Patterns are usually clearer in writing than in memory.
4. Confirm with a clinician. Blood DAO is offered by some private labs but the levels do not correlate well with symptoms. Diagnosis remains clinical.

Histamine intolerance is often confused with allergies, IBS, and mast cell activation syndrome (MCAS). True allergy is an IgE-mediated immune reaction with consistent and rapid symptoms (often anaphylaxis). MCAS is a separate, much rarer condition involving abnormal mast cell behaviour. IBS shares many symptoms but does not respond to a low-histamine approach. If a reaction ever involves breathing difficulty or swelling of the face, lips or throat, that is emergency territory - call 999 in the UK or 911 in the US if it is happening now - and it needs proper allergy testing afterwards, not self-management as histamine intolerance.