WELL;
Food allergies can affect anyone at any time. Children under age 3 frequently have food allergies but they tend to lose their sensitivity as they get older, usually by age 4 or 5. It is common for adults to become allergic to foods that they tolerated for years. Generally, people who are susceptible to other allergens, such as those who suffer asthma, allergic rhinitis (hay fever) and dermatitis, are more likely to experience food allergies. While significant food allergies affect approximately 2 percent of the population, most people experience only mild reactions.
The symptoms of food allergies are a function of the immune system. The process by which food causes an inappropriate or exaggerated reaction of the immune system is not yet understood. Normally, the immune system forms antibodies and sensitized white blood cells that destroy viruses and bacteria by recognizing foreign proteins on the surfaces of these microorganisms. When the immune system misidentifies harmless substances as potentially harmful, it forms antibodies against them, causing allergic symptoms. In adults who develop allergies to previously tolerated foods, the immune system may have changed or the immune system may now recognize a food as foreign due to a change in the intestinal barrier to absorption of intact food proteins. The digestive system normally protects against food allergy by producing enzymes that break down food into small molecules, which are unable to stimulate the immune system and cause an allergic reaction.
Food allergy symptoms depend more on the person than the food, and symptoms vary greatly in type and severity. The most common symptoms are vomiting, diarrhea, hives and sometimes nasal discharge or asthma. People also can experience an oral allergy syndrome with symptoms of itching and sometimes swelling in the mouth and throat. Oral allergic reactions usually occur on exposure to fresh, not cooked, foods. Asthmatics are more likely to have wheezing reactions to problem foods. Asthmatics who are allergic to peanuts may experience a reaction simply by skin contact. Some people may be so sensitive to fish allergens that they experience a reaction if they enter a room that smells of fish! Most food allergy symptoms are experienced immediately, usually within 20 minutes, although some may not occur for several hours.
Because food allergy symptoms often are similar to those caused by other conditions, food allergies can be difficult to diagnose, especially in infants. A baby with vomiting or diarrhea may be allergic to cow's milk, or may have another condition such as esophageal reflux, caused by an inefficient muscle valve at the end of the esophagus that allows the contents of the stomach to flow back into the esophagus. People who experience diarrhea or gas when they consume milk, cheese, or foods containing them, may be deficient in the enzyme lactase, which is needed to digest lactose, one of the sugars present in milk; the diagnosis can be confirmed with lactose-challenge testing (the patient is given a test dose of lactose to swallow and observed for symptoms).
While food allergy symptoms usually are mild, some reactions can be dangerous. Anaphylaxis is a rare, severe and sudden life-threatening allergic reaction to food that causes shock, sudden lowering of blood pressure, or airway obstruction in the throat or lungs, requiring immediate medical attention. Those who have suffered previous severe reactions to foods should carry an epinephrine kit, which contains a preloaded syringe of epinephrine (a naturally occurring hormone that is also called adrenaline) that can be promptly injected to treat the reaction.
Answered by
Kishore
, an ibibo Master,
at
8:34 PM on September 28, 2008
