Imagine for a minute you’ve just gone grocery shopping. You bought canned tuna without checking the sell-by date, and it’s past its prime. You decide to risk it and eat it for dinner. Within an hour, you get a stomachache, hives, and nausea: all symptoms common to allergic reactions. Do you have an undiagnosed fish allergy? Maybe, or it could be something else entirely: histamine poisoning.
How do histamines work?
For those familiar with allergies, you’ve probably heard of histamine, or at least antihistamines. Histamine is an important signaling molecule in the immune response. It triggers a range of effects such as stimulating mucus production, increasing blood flow, and constricting the lung muscles—symptoms that overlap with those of an allergic reaction. The histamine in our bodies usually comes from breaking down histidine, one of the nine essential amino acids. Our body uses histamine as needed, then digests the rest with one of two enzymes: DAO and HNMT. These enzymes convert the remaining histamine into other molecules, which are used for other biological functions or expelled.
However, there are several foods that contain already-formed histamine, like fish and fermented foods. When we eat these foods, we usually aren’t ingesting enough histamine to cause harm, as those enzymes in our intestine (primarily DAO) can get rid of a decent amount before it enters the bloodstream. However, if the DAO can’t keep up with the histamine, you’re at risk of histamine poisoning. This can either happen because you’ve eaten excess amounts of histamine—like in expired tuna—or because you have a histamine intolerance, a condition where your body either has insufficient or malfunctioning DAO.
As histamine is the driver of many allergic symptoms, histamine poisoning causes many of the same symptoms as allergies—flushed skin, diarrhea, itchiness, and in rare cases, breathing and heart problems. These symptoms usually fade within two days and are very rarely life-threatening. Unfortunately, due to the overlap in symptoms with allergies, it can be difficult to accurately diagnose histamine poisoning.
What can you do about histamine poisoning?
Similar to many allergy-like conditions, your best bet is avoidance—fewer fermented foods and no expired fish. Treatment for histamine poisoning, aside from waiting it out, often includes taking antihistamines, and in more severe cases, medications like epinephrine.
Before we fin-ish 😉, here are some “fun” facts about histamine poisoning and histamine intolerance:
98% of histamine poisoning cases come from fish—the disease is often called scombroid poisoning, after the fish family Scombridae, where the association between poisoning and fish was first noticed.
Histamine poisoning is one of the only food poisonings caused by ingesting a small molecule, rather than bacteria or viruses.
Histamine is more concentrated in older foods because bacteria break down histidine to make histamine in much the same way we do.
Histamine is heat-stable, so you can’t get rid of it by cooking/heating up the food.
A whopping 80% of people with histamine intolerance are women!
So, if you decide to risk it and eat that can of recently-expired tuna, it’s good to know the facts about histamine poisoning—just in case.
— Nazir and the Allergy Amulet Team
Nazir and the Allergy Amulet Science Team