Some call it the 'chinese restaurant syndrome,' and most people have heard of it: It's a sensitivity to the flavor enhancer called MSG.
What many people don't know is that monosodium glutamate is in a wide range of cuisines and food products, and it's not always easy to tell how much of the additive you're getting.
Sometimes touted as a salt substitute, MSG-like flavor enhancers have more than a dozen names that most people wouldn't look for or recognize. And recently, when some soup makers began advertising their products as "MSG free," its critics began to speak out again.
Activists like Jack Samuels consider it a public health hazard.
He says some people may get headaches, and feel nauseous or fatigued. But for him, and others like him, he says it's far more severe.
"I started to collapse in certain restaurants," Samuels said. "I would feel it coming on and would excuse myself, rush to the washroom and lose consciousness."
Samuels now avoids all processed food, and even grinds his own flour and makes his own bread.
While doctors and dietitians agree that MSG intolerance exists, they largely describe the symptoms as rare, temporary and without long term health consequences.
A spokesperson for the American Dietetic Association, Dawn Jackson Blatner, says severely asthmatic individuals may have trouble with it, but she believes you can only overdose on MSG if you're downing huge quantities in liquid form, like soup.
In fact there are numerous studies that show that in reasonable amounts MSG is safe to eat.
The problem, say critics, is that it's not clear what's a reasonable amount.
Because the government puts MSG in the same general category as salt, there are no limits on how much a manufacturer uses, and no recomended daily amount. Even if there were, it's hard to judge how much you're getting in processed foods: you might read the nutrition label, but most people wouldn't know names like yeast extract, sodium caseinate and hydrolyzed protein.
They're also flavor enhancers, which work much like MSG.
There are varying estimates of how long it takes to be affected, but University of Chicago gastroenterologist Dr. Karen Kim says it should be within twelve or thirteen hours. If you keep a food diary, and that icky feeling always shows up within twelve or thirteen hours of eating certain foods, that may be a clue.
You can also bring a list of MSG like flavor enhancers to the store with you, if you decide that avoiding it entirely is the best course. And whenever you're out to dinner, ask the wait staff about whether or not the kitchen uses MSG-- you can always see if the dish can be made without it.