Individuals who display idiosyncratic reactions to foods show a link between ingestion of such foods and their illness but without any defined mechanisms. The symptoms associated with idiosyncratic reactions can be from trivial to life threatening. For many cases, the role of specific food ingredients in causing idiosyncratic reactions remains to be determined. An example of a well-established idiosyncratic reaction is sulfite-induced asthma. Sulfites are widely used as food ingredients to control nonenzymatic and enzymatic browning and to prevent bacterial growth. Sulfites also are useful antioxidants and can condition dough and bleach certain foods. In some asthmatic populations, sulfite ingestion initiates an asthmatic reaction, which can be severe, and, on occasions, life threatening. The most severe asthmatics seem to be the individuals who are most sulfite sensitive. Tartrazine sensitivity has been reported to cause asthma in some children. A high dose of monosodium glutamate (MSG) affects small populations.