Common Food Allergy Triggers & Where They Hide


People with food allergies must thoroughly examine food labels.


Common Food Allergy Symptoms

Peanuts are one of the most common food allergies.

When the body has an immune system reaction to a specific food, it produces antibodies to that food. When you eat that food, an immune response is triggered, your body releases histamines and you have allergic symptoms. These symptoms may occur immediately after eating the specific food, or up to hours later. Food allergy symptoms may include:

  • skin rash
  • hives
  • swelling of the tongue or throat
  • breathing problems including asthma
  • vomiting or diarrhea
  • abdominal pain

In severe cases, the allergic reaction may result in a drop in blood pressure, loss of consciousness, or death.

Food Intolerance

A common type of food intolerance is lactose intolerance.


To help your doctor figure out if you have food allergies or intolerances, keep a food diary and note what you eat, along with symptoms you experience. Skin tests or blood tests may be ordered to determine food allergies. Food intolerances and food allergies are dealt with differently.

Foods That Cause Allergies

A variety of food groups.

The only way to prevent an allergic reaction to a food is to avoid that food. If you are allergic read labels carefully and when in restaurants ask about ingredients in the food you order.

  • Milk (mostly in children)
  • Eggs
  • Peanuts
  • Tree nuts (like walnuts and pecans)
  • Soy
  • Wheat
  • Fish (mostly in adults)
  • Shellfish (mostly in adults)

Milk Allergies

People with milk allergies should avoid these foods and ingredients.

A milk allergy is different than lactose intolerance. When one is allergic to milk it's a reaction to milk proteins such as casein. Some people cannot drink cow's milk but might be able to drink goat's milk. Others cannot have any type of milk. Symptoms of milk allergy include stomach pain, diarrhea, hives, or difficulty breathing. With lactose intolerance, people cannot digest the sugar (lactase) in dairy. They may experience bloating or gas, but not allergic reaction symptoms.

Read labels carefully. Aside from milk, look for ingredients such as casein or whey, which are components of dairy milk. They may be found in products you may not associate with having dairy in them such as instant mashed potatoes and baked goods.

Egg Allergies

People with egg allergies should avoid these foods and ingredients.

Egg allergies are usually mild, but can be triggered by small amounts of egg. Some people are allergic to the egg white (albumen), and others are allergic to the yolk. In rare cases, severe egg allergy can lead to anaphylaxis. Read ingredients and look for egg on the list. In some cases when there are only small amounts it may not be listed. Some products state they "may contain" egg or other ingredients. Avoid these products if they cause reactions.

Some foods that may contain egg that might not be readily apparent include some types of noodles, processed meats, bagels, pretzels, and other baked goods. In some cases it may not always be listed on the packaging. Contact the manufacturer if you have questions about how a product is made.

Peanut Allergies

People with peanut allergies should avoid these foods and ingredients.

A common food allergen is peanuts, and people with peanut allergies can have severe reactions, which is why they are often banned from classrooms. Some people are so sensitive even shaking the hand of someone who has just eaten the nuts can cause a reaction. In some cases the reaction is so severe the people can go into fatal anaphylaxis.

Peanuts are used in a wide variety of foods including ice cream (as a flavoring), marinades, snack foods, cookies, baked goods, and candy. African, Chinese, Indonesian, Mexican, Thai, and Vietnamese dishes often contain peanuts as an ingredient. Peanuts are also used as a thickener in prepared foods, and peanut oil may be used in many fried and prepared foods.

Tree Nut Allergies

People with tree nut allergies should avoid these foods and ingredients.

Some people with peanut allergies must also be careful of other types of nuts. Peanuts are technically a legume (a bean) that grows underground, but those with peanut allergies may also have allergic reactions to some tree nuts. Almonds, walnuts, hazelnuts, Brazil nuts, cashews, pecans, pine nuts, macadamia nuts, coconuts, chestnuts, and lychee (lichee) nuts should be avoided. Read labels and keep in mind that many of these nuts are hidden not just in foods, but non-food products such as lotion or shampoo.

Wheat Allergies

People with wheat allergies should avoid these foods and ingredients.

An allergic reaction to wheat is actually an intolerance to gluten, which is a protein found in wheat, rye, barley, and oats. Gluten intolerance is associated with "gluten-sensitive enteropathy" or "celiac disease." With celiac disease, the immune system responds abnormally to gluten and the immune response caused by celiac disease is different than the response caused by other food allergies. Symptoms of celiac disease include gas, bloating, diarrhea, weight loss, fatigue, and sometimes vomiting.

People with celiac disease must read labels carefully and learn which products tend to contain gluten. Even gluten-free bread may contain small amounts of wheat. Wheat can also be found in and ale, beer, bourbon, whiskey, and even wine. Many medications in tablet form have a wheat binder not listed on the label. If you have a wheat allergy, ask your doctor or pharmacist for a liquid form or a tablet that uses potato or corn starch.

Soy Allergies

People with soy allergies should avoid these foods and ingredients.

Soybeans are used widely in food processing. Soy flour can be found in various food products from baked goods and breads, to ice cream, breakfast cereal, frozen dinners, salad dressings, mayonnaise, margarine, sausages, hamburgers, other meat products, and even baby foods. Many of these products do not list "soy" on the ingredient labels, but works such as "hydrolyzed protein," "lecithin," "texturizer," "emulsifier," "protein filler," or "extender" will indicate there is soy in them.

Fish Allergies

People with fish allergies should avoid these foods and ingredients.

It's easy to avoid fish if you have a fish allergy. When dining out, there is a risk of contamination from other foods. Ask that your food not be cooked on the same surface or in the same oil as fish. Read labels because some products such as dressings or sauces may contain fish proteins.

Shellfish Allergies

People with shellfish allergies should avoid these foods and ingredients.

People who have shellfish allergies must avoid all types of shellfish. Often people allergic to one kind of fish have "cross-reactivity," meaning they may be allergic to similar foods. For example, if you are allergic to shrimp you will probably have allergic reactions to crab, lobster, and crayfish.

While shellfish is not a commonly hidden ingredient, you will need to pay attention to certain foods. Many Asian dishes contain shellfish. Some imitation shellfish contains flavoring made from real shellfish. Finally, Caesar salad dressing and chili may contain shellfish.

How Are Food Allergies Diagnosed?

A woman talks to her doctor about her food allergy.

To diagnose a food allergy, the first step is usually to keep a food diary. Note what you eat and the symptoms that follow. Next, your doctor will likely recommend eliminating the foods that seem to trigger the allergic reactions. Sometimes a doctor will supervise something called an oral food challenge, where the allergic person is exposed to the suspected food.

Other tests may include a radioallergosorbent blood test (RAST) to check the number of antibodies produced by your immune system, which can help identify specific allergens. An allergy skin test, or prick-puncture test, may also be performed to help identify what is causing the allergic reactions.


A woman reads the ingredients on a food package.

Food allergies are reactions of the immune system to specific foods. Common foods that cause allergic reactions include shellfish, milk, eggs, and peanuts. Hives, asthma, abdominal symptoms, lightheadedness, and anaphylaxis can result from an allergic reaction to a food.

A doctor will determine whether the reactions to the trigger foods are actual allergies or food intolerances, which are more common and treated differently. Once the specific food allergies are identified patients can work with their doctors to manage their allergies.



  1. iStockPhoto
  2. iStockPhoto
  3. iStockPhoto
  4. iStockPhoto
  5. iStockPhoto
  6. iStockPhoto
  7. iStockPhoto
  8. iStockPhoto
  9. iStockPhoto
  10. iStockPhoto
  11. iStockPhoto
  12. iStockPhoto
  13. BigStock
  14. iStockPhoto


  • UpToDate: "Patient Information: Food Allergy Symptoms and Diagnosis (Beyond the Basics)."
  • UpTodate: "Patient Information: Food Allergy Treatment and Avoidance (Beyond the Basics)."