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Food allergy refers to the body’s abnormal immune reaction to foods that would usually be harmless. In the case of food-allergic individuals, the immune system incorrectly identifies food proteins as harmful and launches an immune response to attack them. The severity of a reaction ranges from mild itchiness of the mouth, for example, through to severe and life-threatening anaphylaxis.

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According to estimates, 32 million Americans are living with a food allergy, 5.6 million of whom are children under the age of 18. Approximately 40% of food-allergic children are allergic to more than one food.

To help Americans avoid risky foods and allergic food reactions, the FDA enforced the Food Allergen Labeling and Consumer Protection Act of 2004, which requires that food labels name any major food allergens that are used to make the product.

While more than 170 foods have been recognized as reaction-inducing among people with an allergy, the eight most common allergenic foods recognized by the law are described below. These foods account for 90% of reactions and are often the foods from which other allergenic ingredients are derived.

Milk

Between 2% and 3% of children younger than three years of age are allergic to milk. Although experts used to think most infants would outgrow this allergy by the time they turned three, recent studies have shown that fewer than one-fifth outgrow it by age four. Still, approximately 80% of children are likely to have outgrown the allergy before the age of sixteen.

People who are allergic to cow’s milk may also be allergic to milk from other animals such as sheep and goats.

Milk allergy is not the same thing as lactose intolerance, which is very common. Lactose intolerance is the inability to digest the sugar in milk because some people lack the lactase enzyme. The associated discomfort and diarrhea are not an allergic reaction.

Eggs

Egg allergy is the second most common food allergies among children in US, next to cow’s milk. The majority of children eventually outgrow the allergy. People who are allergic to chicken eggs may also be allergic to other types of eggs, such as duck, goose, or quail.

Eggs are an ingredient found in many foods, ranging from salad dressing, canned soups, and ice cream through to meat-based dishes such as meatballs and meatloaf. Even some egg substitutes on the market can contain egg protein. People with an egg allergy, therefore, need to be extremely vigilant about checking food labels and the ingredients in foods people have prepared for them.

Whether a person has an allergy to egg whites or egg yolks, they should avoid eggs altogether because it is impossible to ensure complete separation of egg white from egg yolk.

Finned fish

The estimated prevalence of finned fish allergy in the United States is 0.4%, and the allergy is usually lifelong. Around 40% of those with this allergy first experience a reaction to fish during adulthood. The most common culprits are salmon, tuna, and halibut. More than 50% of people who are allergic to one type of fish are also allergic to other types of fish. Finned fish allergy is not connected to shellfish allergy; having one of these allergies does not necessarily mean a person has both allergies. However, people who are allergic to fish should avoid seafood restaurants, where there is a high risk of cross-contact between finned fish and shellfish. Fish markets and any areas where fish are being cooked should be also be avoided.

Shellfish

Shellfish allergy most commonly arises during adulthood but is also the third most common allergy among children in the United States. About 60% of people with this allergy first experience a reaction as adults, and the allergy is usually lifelong.

There are two groups of shellfish: crustacea (e.g., shrimps, crabs and lobster) and mollusks (e.g., clams, mussels, and oysters). The crustacean allergies account for the greatest number of reactions, which tend to be severe. Many people with an allergy to crustacea can eat mollusks without experiencing any problems, but anyone with a specific shellfish allergy should consult an allergist before eating any other type of shellfish. Fish restaurants or markets where different types of shellfish are often stored together should be avoided.

Tree nuts

Tree nut allergy affects about 1.1 % of children and 0.5 % of adults in the United States. It is the second leading cause of severe allergic food reactions, and the estimated prevalence of tree nut anaphylaxis (life-threatening reaction) among children is 0.25% to 0.95%

Allergies to tree nuts such as almonds, walnuts, or cashews usually last a lifetime, with fewer than 10% of people with a tree nut allergy outgrowing it.

People often confuse peanut allergy with a tree nut allergy, but peanuts are legumes that grow underground and not true nuts. However, studies show that up to 40% of people with a peanut allergy also react to at least one type of tree nut. People with a tree nut allergy do not need to avoid coconuts, which is a fruit rather than a nut, even though the FDA classifies coconut as a tree nut. Although coconut allergies have been recorded, most people with a tree nut allergy can safely eat coconuts.

Peanuts

An allergy to peanuts is among the most common food allergies found in children in the United States, and peanut is one of the food allergens most commonly associated with anaphylaxis. Since awareness about the number of peanut allergy cases reported has risen, many schools have chosen to be “nut-free” or have designated seating areas for children with peanut allergy to eat their meals so that they will not contact others’ food that may contain peanuts.

In 2017, the National Institute for Allergy and Infectious Disease released updated guidelines about how to classify infants as high, moderate, or low risk for peanut allergy, as well as how to proceed with introducing peanuts to the diet based on the risk level.

Wheat

Wheat allergy is most common in children, with prevalence amongst the United States pediatric population somewhere between 0.4% to 1.0%. Most children outgrow the allergy before they reach adulthood; one-third outgrow it by age four, and two-thirds outgrow it by age twelve.

Wheat is the most commonly produced grain in the United States. Children with a wheat allergy can still eat a wide variety of foods, but the source of grain must be something other than wheat, such as barley, corn, oat, rice, or rye.

Soybean

As is the case with adults, soy allergy prevalence among children is the lowest of the eight major allergens. The allergy affects about 0.4% of children in the United States. Children often outgrow the allergy by the age of three, and the majority have usually outgrown it by the age of ten.

Soybeans are a member of the legume family, but being allergic to soy does not mean an increased risk of allergy to other legumes such as beans, peas, lentils, and peanuts.

Written by

Sally Robertson

Sally has a Bachelor's Degree in Biomedical Sciences (B.Sc.). She is a specialist in reviewing and summarising the latest findings across all areas of medicine covered in major, high-impact, world-leading international medical journals, international press conferences and bulletins from governmental agencies and regulatory bodies. At News-Medical, Sally generates daily news features, life science articles and interview coverage.