While symptoms may appear similar, monosodium glutamate (MSG) sensitivity is not a true food allergy because there is no response by the immune system to MSG.

There are both short and long term health effects, however, reportedly experienced by MSG sensitive individuals. Since physicians, researchers and governmental agencies disagree as to how to diagnosis and treat MSG sensitivity, symptoms may be difficult to define specifically or authenticate. 

According to the National Library of Medicine (NLM) and the U.S. Food and Drug Administration (FDA), some common signs and symptoms of MSG sensitivity include:

• Headache
• Chest pain
• Sweating
• Flushing
• Burning or numbness inside or around the mouth
• Burning or numbness in the back of the neck 
• Facial pressure or tightness
• Tingling, warmth and weakness in the face, temples, upper back, neck and arms
• Shortness of breath
• Weakness
• Rapid heartbeat
• Nausea
• Drowsiness

These signs and symptoms are temporary and typically appear shortly after large amounts of MSG-containing foods have been consumed.  

Asthmatics, according to the Federation of American Societies for Experimental Biology (FASEB) study, may experience the above symptoms as well as breathing difficulty. Additional studies in asthmatics have not produced consistent results to confirm these reported symptoms.

There have been a wide variety of other symptoms attributed to MSG. None of these symptoms have been corroborated by research studies. Uncorroborated symptoms include:

• Migraine
• Heart palpations
• Fatigue
• Hives
• Rash
• Diarrhea
• Bloating
• Joint pain
• Depression
• Insomnia
• Seizures
• Angina
• Hyperactivity
• Neurological disorders