One woman discovered she was allergic to monosodium glutamate (MSG) when she ate Chinese food containing the substance, an ingredient the Food and Drug Administration classifies as generally recognized as safe.

After the meal, the woman’s face swelled, itchy hives and welts erupted on her skin and her air passages closed, stopping her breathing. Emergency room doctors diagnosed her with “Chinese food syndrome.” Although doctors didn’t name MSG as the substance at that time, the woman later identified the culprit after she suffered another allergic reaction of the same kind. This time she’d cooked with ingredients she thought contained no MSG. “But I learned that monosodium glutamate can be present in any number of foods without ‘MSG’ appearing as an ingredient anywhere,” she says.

The lesson here? MSG is also naturally present in other ingredients. Here are a few of them: Autolyzed yeast extract, hydrolyzed vegetable protein, plant protein extract, caseinate, textured vegetable protein, natural flavor and vegetable powder.