21 Ocak 2008 Pazartesi

Food Allergies and Intolerances - Part 1

What is food allergy?

A food allergy causes a specific immunological reaction in the body that can be observed and diagnosed by various tests. An immunological reaction is a reaction against foreign molecules entering the body; normally, its purpose is to protect the body. In the case of food allergy, this reaction is extreme and is provoked by foods that have no adverse effects on most people. These adverse reactions are immediate and localised; common sites are the mouth (swelling of the lips), digestive tract, the airways (wheezing and breathing problems) and the skin (see also anaphylaxis).

What is food hypersensitivity?

Food hypersensitivity refers to all types of overreactions that an organism can have against a food component. Food hypersensitivity can be divided into food allergies and food intolerances. Both refer to abnormal reactions to otherwise safe foods.

What is food intolerance?

Food intolerance is an adverse reaction to a food triggered by a food or food component, e.g. lactose intolerance. It does not involve the immune system. The reaction is due to non-digestion/absorption of a specific food or food component.

For example, people with lactose intolerance do not have the enzyme lactase to digest the sugar, lactose, in milk. This is one of the most common food intolerances occuring in nearly 50% of the adult world population.

Some people have an intolerance against additives such as flavour enhancers (MSG) or preservatives (sulphite). The symptoms vary widely between individuals and it is often impossible to determine which food component causes which reaction.

The symptoms of food intolerance can be mistaken for those of a food allergy. It is important to consult a physician to determine the causes of a reaction to food.

What causes food intolerance?

There is no simple answer. The reason differs from component to component, possible mechanisms are the lack of a particular enzyme (enzymes are needed for specific chemical reactions in the body), heredity, stress or illness, an impaired immune system, environmental pollution and lack of adequate nutrition.

Why are some people allergic to some ingredients?

Family history is one of the best predictors of the likelihood of having a food allergy or intolerance. Children of atopic (=allergic) parents are more likely to have an allergy. Infants with one atopic parent have about twice the risk of developing food allergy as infants whose parents do not have allergies. If both parents are atopic, the risk increases four to six times. For babies that are born into families where close relatives suffer from allergies, exclusive breast-feeding for 4-6 months seems to give some protection.

At what age do symptoms of food allergies or intolerances occur?

A food intolerance or allergy can occur at any age, can be short-term or a lifelong condition. If not identified early food intolerance symptoms can lead to more serious problems in later life: for example, colitis in a child that is caused by lactose intolerance can lead to Crohn’s disease in adulthood.

Who is at risk for food allergy?

Food allergy may appear at any age but true allergic reactions to foods are most common in infants and young children and decrease in frequency with age. It is estimated that about 2% of all adults have a food allergy.

Children of parents who have a history of food allergies have an increased susceptibility to allergies. Children with food allergies should be re-evaluated regularly; often, they outgrow their problems and no longer need restricted diets.

What is anaphylaxis?

Anaphylaxis is a severe allergic reaction — the extreme end of the allergic spectrum. The whole body is affected, usually within minutes of exposure to the allergen. Causes include food, insect stings and drugs.

An anaphylactic reaction is caused by the sudden release of chemical substances, including histamine, from cells in the blood and tissues. The release is triggered by the reaction of the antibodies (immunoglobulin E) with the offending substance (allergen). This mechanism is so sensitive that minute quantities of the allergen can cause a reaction.

In anaphylactic shock, bronchial tissues swell and blood pressure drops, causing choking and collapse. An adrenaline (epinephrine) injection should be given immediately. Adrenaline acts quickly to constrict blood vessels, relax smooth muscles in the lungs to improve breathing, stimulate the heartbeat and stop swelling around the face and lips (angioedema).

Is there a cure for food allergies?

Currently, there are no medications that cure food allergies. Strict avoidance is the only way to prevent a reaction. Most people outgrow their food allergies, although peanuts, nuts, fish, and shellfish are often considered life-long allergies.

What are the most common types of food intolerance?

Lactose intolerance is the most common type of food intolerance. People who suffer from lactose intolerance do not have enough of the enzyme lactase to digest the sugar lactose in milk. Other common types of food intolerance include intolerance of fructose, gluten, alcohol, certain types of fibers and food additives such as flavour enhancers (MSG) or preservatives (sulphite) used in foods.

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