Called at times the Chinese restaurant syndrome, the side effects of eating foods containing monosodium glutamate, or MSG, are similar to those of an allergic reaction. Although less than 15 percent of Americans are sensitive to MSG, according to the University of Illinois Medical Center, in those who are sensitive symptoms range from headaches and nausea to heart palpitations and chest pain.
Eating food containing MSG on an empty stomach increases the risk of the onslaught of MSG symptoms in people allergic or sensitive to MSG because more of the chemical is consequently absorbed into the bloodstream. One of the most frequent adverse reactions reported by MSG sufferers is headache. This can occur anywhere from 30 minutes to several hours after ingesting MSG.
In those sensitive to monosodium glutamate, food that contains MSG can cause abnormal heart rhythms and heart palpitations that show up on electrocardiograms, according to the University of Maryland Medical Center. Rapid, fluttering palpitations and a rapid but steady heart rate are the result of the stimulating effects of MSG on body cells. In those not sensitive to this chemical, MSG stimulates taste, smell and hunger, which is why it is used in processed foods. If nerve cells are over-stimulated, an allergic response can result. MSG can also decrease the amount of air that enters the lungs, causing chest tightness and chest pain.
Excessive sweating and flushing are commonly reported by sufferers as MSG symptoms, according to MayoClinic.com. Because sufficient amounts of air can be inhibited from filling the lungs, wheezing can also occur. Those allergic to MSG may feel weak, dizzy, sick or generally unwell until these symptoms subside, generally in three to four hours.
Those sensitive to MSG can be frightened by feeling numb in the face after eating foods that contain high amounts of MSG. Facial muscles can feel tight or pressured, according to the University of Illinois Medical Center. Muscle tightness and burning sensations can also occur in various parts of the body, including the forearms, neck, chest, abdomen, shoulders and thighs.