TURSDAY October 23, 2008 (foodconsumer.org) -- A new government report estimates that incidence of food allergies in children under age 18 has increased by 18% during the last decade.   Right now four out of every 100 U.S. children suffer food allergies.

The common allergens which account for 90 percent of cases of food allergies include milk, eggs, peanuts, three nuts, fish, soy and wheat, according to the report by the Centers for Disease Control and Prevention.

The CDC does not know why more children now than ever suffer food allergies, but it is known that the immune system has some problem in the individual who has food allergy.

"This seems to be primarily a phenomenon of Westernized countries, among people who have our kind of lifestyle and our kind of diet. You don't see similar things in countries in Asia or in Africa," Hugh Sampson, MD, director of the Jaffe Food Allergy Institute at Mount Sinai Hospital, New York was by WedMD.com quoted as noting.

Food allergies are associated with other conditions.   Among those with food allergies, 29 percent have asthma, 27 percent have eczema or skin allergy, and more than 30 percent have respiratory allergies compared to 12 percent, 8 percent and 9 percent respectively among children who do not have food allergies.

The CDC data come from the National Health Interview Survey of 9,500 children in 2007 and the National Hospital Discharge Survey of 270,000 inpatients from about 500 hospitals.

The report titled "Food Allergy among U.S. Children: Trends in Prevalence and Hospitalizations" was released on October 22.

Food allergy can be life threatening and differs from food intolerance. Food allergy is an abnormal response to a food by the body’s immune system and the latter is not and often does not pose a risk.

The following are some basics about food allergy cited from a government source.

Introduction

Food allergy is an abnormal response to a food triggered by the body's immune system. Allergic reactions to food can cause serious illness and, in some cases, death. Therefore, if you have a food allergy, it is extremely important for you to work with your health care provider to find out what food(s) causes your allergic reaction.

What Is Food Allergy?

An immediate allergic reaction involves two actions of your immune system.

1) Your immune system produces immunoglobulin E (IgE), a type of protein that works against a specific food. This protein is called a food-specific antibody, and it circulates through the blood.

2) The food-specific IgE then attaches to mast cells, cells found in all body tissues. They are more often found in areas of your body that are typical sites of allergic reactions. Those sites include your nose, throat, lungs, skin, and gastrointestinal (GI) tract.

Generally, your immune system will form IgE against a food if you come from a family in which allergies are common, not necessarily food allergies but perhaps other allergic diseases such as hay fever or asthma. If you have two allergic parents, you are more likely to develop food allergy than someone with one allergic parent.

If your immune system is inclined to form IgE to certain foods, you must be exposed to the food before you can have an allergic reaction.

As this food is digested, it triggers certain cells in your body to produce a food-specific IgE in large amounts. The food-specific IgE is then released and attaches to the surfaces of mast cells.

The next time you eat that food, it interacts with food-specific IgE on the surface of the mast cells and triggers the cells to release chemicals such as histamine.

How Do Allergic Reactions Work?

Depending upon the tissue in which they are released, these chemicals will cause you to have various symptoms of food allergy.

Food allergens are proteins within the food that enter your bloodstream after the food is digested. From there, they go to target organs, such as your skin or nose, and cause allergic reactions.

An allergic reaction to food can take place within a few minutes to an hour. The process of eating and digesting food affects the timing and the location of a reaction.

1) If you are allergic to a particular food, you may first feel itching in your mouth as you start to eat the food.

2) After the food is digested in your stomach, you may have GI symptoms such as vomiting, diarrhea, or pain.

3) When the food allergens enter and travel through your bloodstream, they may cause your blood pressure to drop.

4) As the allergens reach your skin, they can cause hives or eczema.

5) When the allergens reach your lungs, they may cause asthma.

Cross-Reactivity

If you have a life-threatening reaction to a certain food, your health care provider will show you how to avoid similar foods that might trigger this reaction. For example, if you have a history of allergy to shrimp, testing will usually show that you are not only allergic to shrimp but also to crab, lobster, and crayfish. This is called "cross-reactivity."

Another interesting example of cross-reactivity occurs in people who are highly sensitive to ragweed. During ragweed pollen season, they sometimes find that when they try to eat melons, particularly cantaloupe, they experience itching in their mouths and simply cannot eat the melon. Similarly, people who have severe birch pollen allergy also may react to apple peels. This is called the "oral allergy syndrome."

In adults, the foods that most often cause allergic reactions include

Shellfish such as shrimp, crayfish, lobster, and crab

Peanuts

Tree nuts such as walnuts

Fish

Eggs

The most common foods that cause problems in children are

Eggs

Milk

Peanuts

Tree nuts and peanuts are the leading causes of deadly food allergy reactions called anaphylaxis.

Adults usually keep their allergies for life, but children sometimes outgrow them. Children are more likely to outgrow allergies to milk or soy, however, than allergies to peanuts or shrimp. The foods to which adults or children usually react are those foods they eat often.

Common Food Allergies

If you go to your health care provider and say, "I think I have a food allergy," your provider has to consider other possibilities that may cause symptoms and could be confused with food allergy, such as food intolerance.