A food allergy is caused by an inappropriate immune system response to a specific food or substance in a food. Your immune system mistakes a food for a harmful substance, releasing immunoglobulin E (IgE) antibodies into your body to fight it. Then, the next time you eat that food—even the tiniest bit of it—the IgE antibodies sense it and cause your immune system to release chemicals to fight it off. These chemicals cause the symptoms of an allergic reaction.

Eight kinds of food cause 90 percent of food allergies. Luckily, the Food Allergen Labeling and Consumer Protection Act, which took effect January 1, 2006, requires food manufacturers to disclose in plain language whether products contain any of these eight types of food:

Milk

Milk allergies are much more common among children than adults; they are especially common among very young children. Milk affects 2.5 percent of children under the age of three, making it the most common childhood food allergy. 80 percent of children with a milk allergy will outgrow it by the time they turn four. Two types of protein in milk can cause an allergic reaction: casein and whey.

Eggs

As with milk, egg allergies are much more common among children than adults. Children tend to eventually outgrow their egg allergies. A number of proteins in both the yolks and whites of eggs can cause allergies; however, allergies to egg whites are more common than allergies to yolks.

Peanuts

Peanut allergies are more common in children than in adults. About 1.2 percent of children are allergic to peanuts. Peanuts are also the cause of the most severe food allergy attacks. It is, therefore, essential to get your child checked for a peanut allergy even after the mildest of reactions to peanuts or peanut butter; even if he or she has only had minor reactions, there is a serious risk for severe attacks in the future. Many food products that don’t contain peanuts are processed in plants with peanuts and may have some peanut proteins in them. Make sure to read food labels carefully if you or your child has a peanut allergy.

Wheat

Four classes of what proteins can cause allergic reactions: albumin, globulin, gliadin and gluten. Wheat proteins, especially gluten, are used in many types of food, including:

  • Bread
  • Cake and muffins
  • Pasta
  • Crackers
  • Beer
  • Ketchup
  • Soy sauce
  • Ice cream
  • Food starch
  • Natural flavorings

Some people have an exercise-related allergy to wheat: they develop symptoms only if they exercise within a few hours after eating wheat. Unfortunately, these people often experience anaphylaxis if their symptoms are triggered. Celiac disease is sometimes incorrectly called a gluten allergy, when it is really a digestive disorder.

Soy

Soy allergies are also more common among children than adults, and most children outgrow their soy allergy by the time they are three. Most of the time, allergic reactions to soy are mild. Because soy is used in many products where its use may not be obvious, it is important to read all food labels if you have a soy allergy.

Fish

Although a person with a fish allergy may be allergic to only one species of fish, it is generally recommended that he or she avoid all fish to be on the safe side. Unlike many other food allergies, fish allergies tend to last a person’s whole life. Fish is often used in food products where it may not be expected, so always read food labels if you have a fish allergy.

Shellfish

All sorts of shellfish can cause allergic reactions: crustaceans, such as crabs, lobster, shrimp, and prawns, and mollusks such as clams, mussels, oysters, squid, and octopus. Some people are only allergic to one kind of shellfish; others must avoid all types. Shellfish allergies are more common among adults than with children.

Tree nuts

Tree nuts that may cause an allergic reaction include almonds, pecans, cashews, pistachios and walnuts. As with shellfish, some people are allergic to only one type of nut, while others have reactions to all.