MSG, or monosodium glutamate, is a commonly used food additive that enhances the flavors of foods. MSG is often found in canned foods, processed meats, Chinese foods and other processed foods. Though there are no MSG-specific allergies, the Merck Manuals Online Medical Library states that some people may be sensitive or intolerant to MSG, presenting with symptoms that mimic an allergic reaction. Symptoms may develop within minutes to hours after ingesting MSG.
Skin Reaction
MayoClinic.com states that some people report feeling flushed or hot in the face or neck after eating MSG. There may also be sweating, itching, and numbness, tingling or a burning sensation in the face, neck and chest.
MSG reactions are generally mild. However, some people experience swelling or tingling around the mouth, lips and tongue, which can result in complications such as trouble breathing; this requires immediate medical attention.
Central Nervous System Reaction
Health Central reports that some people experience a headache after exposure to MSG. The headache may appear as pressure inside the head, and may begin within an hour after eating MSG. A person may also experience dizziness and facial pressure. Health Central states that headache symptoms generally resolve within 2 to 3 hours.
Heart and Breathing Reaction
A person may experience heart palpitations as a fluttering of the heart. MayoClinic.com states that there may also be chest pain or pressure along with an increased heart rate after eating MSG.
Some people also develop shortness of breath in reaction to MSG, and may have wheezing -- a high-pitched, whistling sound with breathing. The amount of MSG consumed may affect how severely symptoms are experienced. These symptoms generally resolve quickly; however, a person who develops chest pain, abnormal pulse or trouble breathing should seek medical attention to avoid complications.