MSG stands for monosodium glutamate; this is a flavour enhancer added to certain foods and also is a natural flavour in seaweed. Adverse reactions to food additives like MSG are relatively common. However MSG is very rarely diagnosed as is never really reported by people, and the rate of reaction is unknown.
An MSG allergy is normally known as ‘Chinese Restaurant Syndrome’ as MSG is rather high in Asian-style foods. Most people who are affected will experience symptoms shortly after eating foods containing MSG. Typical symptoms include numbness on the back of the neck, shoulders and arms; people can have a sense of overall weakness, and heart palpitations can occur, Other symptoms are facial pressure, headaches, nausea, chest pain and drowsiness.