True allergic reaction (IgE mediated) to food must be differentiated from food intolerance, which is rarely multisystemic, not necessarily found among atopic patients, with no positive skin prick tests or in vitro responses (RAST). A nonallergic reaction that typifies food intolerance would be an acute gastrointestinal response in a lactose-intolerant individual.. This patients does not have the enzyme lactase and, therefore, cannot breakdown sugar lactose in milk and other foods into glucose and galactose. Profound diarrhea or vomiting usually results without any other system involved (respiratory or skin, for example). Food avoidance is the treatment of choice, as it is with food allergy, and over time, food intolerance may resolve. Lactaid is a brand of milk in which the enzyme lactase is added so that the milk may be consumed.