Soybeans

Soy's histamine relevance depends a lot on how it's prepared — fermented forms are clearly high in histamine, while the status of plain soybeans is less firmly established.

• Fermented soy is high risk — Products like tempeh, miso, and soy sauce carry significant amounts of histamine from the fermentation process and are consistently flagged across major references

• Plain soy tolerance varies — Some people with histamine intolerance also report difficulty with unfermented soy products, though the evidence for plain soybeans as histamine liberators is not consistent across the scientific literature

Less processed soy products like plain tofu or edamame are generally considered lower risk than their fermented counterparts, though individual responses vary.