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That reaction to seafood may not be an allergy

Lorraine Graves   Jul-20-2018

Fish, like all food kept cold and eaten promptly, is safe to eat.

Photo by Chung Chow

It hits before you put your fork down or perhaps it’s a a few hours later, but the symptoms come on like a tonne of bricks. It’s might seem like an allergic reaction, but often, it’s not. You’ve been poisoned, naturally.

“I’m an avid sushi lover. I first noticed my throat feeling sticky about five minutes into the meal,” says a Richmond resident, who chooses not to have his name published.



“If it is toxin-associated, it can occur very quickly,” says Lorraine McIntyre, food safety specialist for the BC Centre for Disease Control (BCCDC).

What we normally call food poisoning is often bacteria or a virus we eat, which takes time to grow in our digestive tracts to levels that make us sick. That hits many hours later.

But with Scombroid poisoning, McIntyre says, you become ill fast because it is actually a toxin that goes to work right away.

“As someone trained in First Aid, I thought I was having an allergic reaction,” the young man says.

Scombroid is often mistaken for a severe allergic reaction. Frequently, but not always, it hits after eating fish or seafood but McIntyre says, “Less than half of one per cent of the population is actually allergic to fish.”

After a scombroid reaction to fish, many people think they’ve suddenly developed a fish or seafood allergy for life. The good news: if it is a scombroid reaction, it is not the start of a lifelong allergy. The bad news is you’ve been poisoned by food improperly stored, sometime since harvesting.

Something important to remember is that the toxin isn’t destroyed by cooking, freezing or canning.

McIntyre offers the example of a Canadian airport shop that used canned fish to make tuna salad sandwiches. The shop did nothing wrong. “The canned tuna had been temperature-abused somewhere in the food chain.” So the poison remained even in the cooked, canned tuna.

According to McIntyre, bacteria grow on food that has been kept too warm, too long. You can buy an inexpensive fridge thermometer to see if yours works at a low enough temperature, below 4.0 degrees C (40 F).

Some bacteria turn a natural, healthy chemical in food into histamine, the way that yeast turns sugars into alcohol as it grows. Dangerous food may not look or smell off.

Just as too much alcohol can poison a person, too much histamine can act as a toxin. It causes what looks like a vehement allergic reaction. Like alcohol, different people have different sensitivities and reactions. That’s one reason people eating the same food may not react the same. But, drinking alcohol when eating food containing histamine can accentuate the problem.

A report in the New England Journal of Medicine (NEJM) cited a group eating at a restaurant where only some of the diners became ill with scrombroid. When the original fish was tested, some areas of the same fish were definitely off while other parts were fine. Yet another reason why not everyone eating the same dish gets sick.

“One paper I’m looking at says 10 to 18 per cent of the people will become ill,” says McIntyre. In a group of 10, that means one or two people.

As well, some medications or conditions can make people more sensitive to scombroid poisoning.

There is a long list of scombroid symptoms possible. According to McIntyre, “They can mimic some of the allergic symptoms—hives and rash and flushing and facial swelling.

The face and upper torso of the young man The Sentinel spoke with turned bright red.

“You can have a kind of weird peppery or metallic taste, numbness, headache, feel dizzy, or have a pulse that’s rapid,” explains McIntyre. “You might have difficulty swallowing or thirst, facial flushing, sweating, nausea or respiratory distress.”

The person affected says, “My heart was racing and my throat felt like it was starting to tighten.” As it became hard to breath, he says, “I felt scared.”

McIntyre cautions that asthmatics can have trouble breathing. There are also gastric symptoms possible, queasiness or diarrhea.

Often, the diagnosis for scombroid is missed because some medical professionals believe people with scombroid have to have all the symptoms on the list while others believe it is very rare. Neither are true. But says McIntyre, “Just like many other illnesses you don’t have to have all the symptoms. Some will get some symptoms, some others not.” One American source says scombroid is the number 2 cause of nausea and diarrhea after Norwalk Virus.

In the emergency department of a Vancouver hospital, the ill young man was given intravenous (IV) antihistamine which helped and then was told it must just be panic attack. Since he didn’t have hives and because his heart was racing, the doctor said, it couldn’t be allergies. The patient was sent home. He was still bright red. It wasn’t a sunburn.

Most people get all better within a couple of days, as did the young man. The treatment for scombroid is often antihistamines, the same drugs used to calm an allergic reaction, when the body releases extra histamine naturally.

McIntyre advises, “It would depend on how serious the reaction is. If you are having trouble breathing, or your pulse is very rapid, it would be worth going to emerg for supportive therapy.”

If you don’t go to emergency or call 911, McIntyre says you have a couple of 24/7 options for advice in the BC nurse line at 811 or the BC Drug and Poison Information Centre at 1 (800) 567-8911.

The next step according to McIntyre is to be sure to report your reaction to the Vancouver Coastal Health inspectors, even if your doctor or the hospital didn’t agree with your suspicions:

“It’s still worth reporting, even if it’s after the fact,” she says. “Demand inspections after a reaction get priority.” Richmond Public Health can be reached through (604) 233-3147.

A BCCDC report about scombroid outbreak says, “Attack rates in one outbreak were higher for persons who ate lunch at 12:30 p.m. compared to those who ate lunch one to two hours earlier.” In that case, it was food that had been sitting at 30 Celsius.

Another medical report mentioned expensive restaurant portions of tuna kept in a refrigerated drawer. The repeated opening and closing let the temperature climb to unsafe levels. Yet another report mentioned costly sushi cuts that were set out at the end of day at room temperature so they would be thawed by morning.

McIntyre, currently chairing a national working group on fermentation, says scombroid occurs in many different kinds of food not just fish and shellfish, for example, cheese, fermented sauces, wine.

She adds that it isn’t just commercially-produced or restaurant food. Products stored, cooked or fermented at home can also offer scombroid poisoning if not done properly.

McIntyre also offers that how sensitive individuals are to scombroid poisoning varies.

“We investigated a case through the Poison Control Centre. I remember there was a lady who had a reaction to a fermented fish sauce. The fermentation process created this issue. She was quite sensitive and quite ill.”

McIntyre said when the fish sauce was tested, it actually had safe levels of histamine in it. She was just very sensitive. For her, the fresher the better for all foods.

If you are unsure whether it was a scombroid reaction, you can ask to be tested for allergies by a medical doctor.

To prevent scombroid in food prepared at home, the same food handling rules as always apply; keep cold foods cold and hot foods hot. If you want to cook foods most at risk for causing scombroid poisoning with the new and trendy method, a sous-vide, be sure your water bath is over 55 C.

If you suspect scombroid and are very ill, call 911 or seek medical help. Report what you ate, as well as when and where you ate it to the health department. Often, it takes only a small tweak in a restaurant’s food handling to make it safe for everyone.

So, it may not be an allergy after all. If in doubt, check with a medical doctor. If it was a scombroid reaction, to quote the New England Journal of Medicine: “Patients will be able to eat the same (fresher) fish later on.”

And for our young man who had scombroid; how does he feel about sushi now? “I have had it several times since the incident and have been absolutely fine. However, I have not returned to the same restaurant.”

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