Lactose intolerance is the inability to digest significant amounts of lactose, the predominant sugar of milk. This inability results from a shortage of the enzyme lactase, which is normally produced by the cells that line the small intestine. Lactase breaks down milk sugar into simpler forms that can then be absorbed into the bloodstream. When there is not enough lactase to digest the amount of lactose consumed, the results, although not usually dangerous, may be very distressing. While not all ...

food allergy is hypersensitivity to dietary substances, leading to various types of gastrointestinal complaints. It occurs mainly, but not exclusively, in children. It is a common type of allergy, and is usually treated with an exclusion diet.