What you want to ask is whether the histamine content of stale salmon is high? Fresh salmon has high histamine content. The histamine content of stale salmon may be higher than that of fresh salmon, because histamine is a biogenic amine, which exists in seafood such as salmon. If seafood is not treated in time or stored improperly, the histamine content will gradually increase. Eating high levels of histamine may lead to food poisoning, manifested as headache, dizziness, vomiting, diarrhea and other symptoms.