I hear about that almost every day. It's interesting since it requires protein for a food allergy reaction. MSG does not contain protein. It does contain an amino acid and glutamate which numerous scientific and government bodies around the world have extensively studied over the last 100 years. There's no difference between the two in our bodies.
People often complain of Chinese restaurant syndrome, but think about it for a minute.
Glutamate, which provides rich flavor to foods from msg, occurs in virtually every food that contains protein. Rich sources of glutamate include mushrooms, parmesan cheese, tomatoes. I've never heard anyone complain of an Italian restaurant headache, or syndrome. And one probably eats more glutamate in an Italian dish than they would in a Chinese dish. The only time that a food might exacerbate hyperactivity disorder is if a child has a food allergy in addition to the hyperactivity disorder.