Last updated: April 2026
Histamine intolerance (HIT) is impaired histamine breakdown in the body caused by reduced activity of diamine oxidase (DAO), or in some cases by histamine-N-methyltransferase (HNMT) pathways. Histamine is a biogenic amine naturally present in many foods and is formed especially through fermentation, aging, and microbial activity.
Estimated HIT prevalence in the population is 1-3% (Maintz & Novak, 2007).
A physician makes the actual diagnosis of histamine intolerance after excluding other possible causes of symptoms and assessing the clinical picture. An elimination diet, food diary, or DAO activity test may give the physician supporting information, but none confirms the diagnosis on its own. Histamin.io is an orientation aid and does not diagnose histamine intolerance.
Each food in the database has a primary rating and optional additional flags that describe the intolerance mechanism.
| Label | Description |
|---|---|
Suitable | Low histamine and low biogenic amine content; the food does not trigger histamine release from cells. Suitable for everyday use. |
Caution | The food may contain a moderate amount of histamine or may only be tolerated individually in small amounts. Track your own reactions. |
Unsuitable | High histamine content or high levels of other biogenic amines such as tyramine or putrescine. We recommend excluding it from the diet. |
A food can have a primary rating plus one or more additional flags. The flag describes why the food may be problematic, because different patients react differently to different mechanisms.
| Icon | Flag | Description |
|---|---|---|
| Liberator | The food can trigger histamine release from mast cells regardless of its own histamine content. Typical examples include strawberries, citrus fruits, tomato, avocado, egg white, and seafood. | |
| Biogenic amines | The food contains higher levels of other biogenic amines, such as tyramine, phenylethylamine, or spermine. They may act similarly to histamine and cause similar symptoms. Typical examples include chocolate, banana, walnuts, and cashews. | |
| DAO blocker | The food inhibits diamine oxidase, the enzyme that breaks down histamine in the digestive tract. This can slow histamine processing from all foods eaten at the same time, so the effect may multiply. Typical examples include alcohol, black tea, green tea, mate, and energy drinks. | |
| High-protein decay risk | For rapidly perishable high-protein foods, storage and repeated reheating can increase histamine load, and reheating does not destroy the histamine formed. In the diary, marking the food as stored or reheated treats it as unsuitable, while the catalog rating applies to the fresh food. |
Flags are shown as small icons on the food card. Expanding the card shows the detailed explanation.
Food ratings are based primarily on these sources:
For each food, the available sources are compared. When sources disagree, we use the more conservative rating, meaning the stricter classification. The Why field for each food gives a short explanation of the rating and points to the mechanism: histamine content, tyramine, liberator effect, DAO inhibition, or another relevant reason.
The database is updated when new scientific recommendations are published or when a mismatch with practice is found.
Histamine tolerance is highly individual. A food marked as caution may cause symptoms in one person and be tolerated by another. The database is an orientation aid, not a binding meal plan. For a personal diet plan, consult a physician or registered dietitian.
