How bad is it for you?
Neurological Disorders involving the nervous system like Alzheimer's and Parkinson's. MSG is associated with sending signals to cells in the brain but with to much MSG it can malfunction and send different signals to the central nervous system. MSG can also over stimulate nerve cells until they die. It is a neurotoxin that can cause damage to the brain.
Long Term Effects include, obesity, gonadal dysfunction (hormone dysfunction), learning difficulty. There was a study on the long term effects on the liver following MSG injections. The changes in the liver after 75 days, in the mice showed variable changes. Areas around central veins were most affected. The liver cords were disrupted. Even normal looking cells showed depletion of PAS +ve material in the cytoplasm. The long term effect on the liver showed moderate and patchy hepatocellular damage.
Allergic Response- MSG may directly affect the immune response by stimulating or damaging the nervous system. Off of a health allergy website, it quotes, "that some people could be sensitive to MSG presenting symptoms of allergic reactions."