Food allergy: Signs and types. The image is a pile of peanuts.

Food allergy: Symptoms and types

From food allergy symptoms to allergy testing, an allergist discusses the eight most common food allergies
May 10, 2019

It can be hard to recognize if you have a food allergy. Roughly 5.6 million children and 26.4 million adults in the United States have a food allergy. A food allergy is an abnormal response to a food triggered by your body’s immune system. These responses, or allergic reactions, can potentially be life-threatening. The Food Allergy Research and Education (FARE) notes 170 foods have been reported to cause allergic reactions. However, only eight types of food account for 90 percent of all food allergy reactions. Susan Andrew, MD, allergist-immunologist, clinical assistant professor at the Texas A&M College of Medicine, explains how you can recognize if you have a food allergy. 

Symptoms of a food allergy

“Although some allergies can lead to itchy skin or rash, other allergies can cause severe reactions such as swollen throat or anaphylaxis,” Andrew said. “Anaphylaxis is a severe response that affects blood pressure and breathing and can even lead to death.”

Symptoms of a food allergy manifest in the skin, gastrointestinal tract, cardiovascular system and respiratory tract. Common symptoms of a food allergy include:

  • Vomiting and/or stomach cramps
  • Hives or a raised, itchy red rash
  • Wheezing
  • Trouble swallowing and swelling of the tongue
  • Dizziness or feeling faint
  • Anaphylaxis

Just because an initial allergic reaction to a food allergy was mild, the second reaction to the food allergy can still be severe.

How long do food allergy symptoms last?

Most food allergy related symptoms often start within minutes of ingestion, but some first symptoms can occur within two hours. Sometimes food allergy symptoms come in a second wave, which is called a biphasic reaction. The second wave of allergy symptoms can occur four to six hours after the ingestion of the allergen, so people, especially young children, need to be kept under close observation until then.

Milk allergy: The difference between a milk allergy and lactose intolerance

A milk allergy is when the immune system does not recognize dairy and attacks it by releasing histamines. Someone with a milk allergy can develop severe symptoms, such as breathing complications or an uneven heartbeat.

“A milk allergy is not to be confused with lactose intolerance,” Andrew said. When someone is lactose intolerant, lactose—a type of sugar found in dairy products—moves through the large intestine without being properly digested. It can lead to uncomfortable symptoms such as gas, bloating or indigestion. “When someone is allergic to milk and dairy products, the symptoms affect more than the digestive tract.”

Tree nut allergy: Which nuts are tree nuts?

Common tree nuts are walnuts, almonds, hazelnuts, cashews, pistachios and Brazil nuts. FARE suggests tree nut allergies tend to be lifelong. Only nine percent of children with a tree nut allergy will out grow it.

Similarly, younger siblings of children who are allergic to tree nuts are at higher risk of developing the same allergy. Furthermore, 25 to 40 percent of individuals with a tree nut allergy are also allergic to peanuts.

Peanut allergy: Peanut allergies on the rise

Although peanuts may sound like they are a tree nut, they are actually grown underground and are a legume. Peanut allergies are common childhood allergy that can linger into adulthood. However, studies show about 20 percent of children will grow out of their peanut allergy.

“Peanuts often come into contact with tree nuts during manufacturing and serving processes,” Andrew explained. “For this reason, some health care providers may tell their patients with allergies to avoid both peanuts and tree nuts.”

Soy allergy: Soybean allergy is very common, especially in babies and children

Often people hear soy allergy and think they can avoid it by skipping soy sauce and tofu. However, soy may be found in many unexpected places like mayonnaise, Worcestershire sauce and vegetable broths.

“If you are eating at a restaurant, tell your waiter about your soybean allergy to make sure that the chef does not cross-contaminate while preparing your meal,” Andrew said. Soy is a common ingredient in Chinese, Indian, Indonesian, Thai and Vietnamese food, so cross-contamination very likely at those restaurants.

Fish allergy: A fish allergy is not the same as a shellfish allergy

Although most food allergies develop early, fish is one of the few that often develops in adulthood. FARE reports about 40 percent of people with a fish allergy experience their first allergic reaction as an adult.

More than half of people who are allergic to one type of fish are also allergic to other fish. The most common fish that people with a fish allergy cannot eat are salmon, tuna and halibut.

Shellfish allergy: A shellfish allergy is not an iodine allergy

If you are allergic to shellfish, then you not necessarily are allergic to fish or iodine. However, in many circumstances, cross-contamination between fish and shellfish is likely, so take extra precaution when preparing or ordering fish.

People with a shellfish allergy should avoid crustaceans like shrimp, lobster and crab. Many people who have a shellfish allergy can tolerate mollusks like scallops, oysters, clams and mussels.

Wheat allergy: A wheat allergy is different than celiac disease

A wheat allergy is different from celiac disease, which is an immune reaction to eating gluten—a protein found in wheat, barley and rye. While a wheat allergy includes an allergic reaction to gluten, other grains like barley, rye and oats may be safe to eat. A majority of children who have a wheat allergy will outgrow it, whereas celiac disease will last throughout someone’s life.

A wheat allergy will cause your body to negatively react to the allergen. Celiac disease will cause your body to attack its own villi—components of the small intestine that are responsible for absorbing nutrients. It is important to get an accurate diagnosis of your condition, and a candid talk with your health care provider can get you on the right track.

Egg allergy: Someone with an egg allergy can get a flu shot

The American College of Allergy, Asthma and Immunology estimates as many as 2 percent of children are allergic to eggs. They also estimate as many as 70 percent of children with an egg allergy outgrow the condition by age 16. “Egg is a common ingredient in many foods, so people with an egg allergy must always remain vigilant and carefully read food labels,” Andrew said.

In the past, the flu vaccine contained a small amount of egg protein. Now, the flu vaccine contains no egg, so individuals with an egg allergy can and should get the vaccination.

Food allergy tests

If you think you have a food allergy, speak with your health care provider. You may have only had a minor reaction the first time, but the reaction could be severe the next time. Avoid the suspected food, and start a food diary until your appointment. Write down everything you eat as well as any symptoms you have and how long the symptoms last.

Your health care provider may suggest an allergy test. “Allergists or immunologists usually test allergies by a skin or blood test,” Andrew said. “Skin tests are more popular, because they give almost immediate results. However, if a patient is taking a medication that may interfere with results or has a severe skin condition like eczema, the blood test may be recommended.”

A skin allergy test consists of many small pricks of needles that barely penetrate the skin. Each needle has a different allergen on the tips. If your body reacts to one prick, then that identifies you are allergic to that specific allergen. 

“If you think you have an allergy, speak to a health care provider. Food allergies can be dangerous if you are taken by surprise,” Andrew said. “If you have severe reactions, have a contingency plan like an epinephrine auto-injector ready in case you accidentally expose yourself.”

— Mary Leigh Meyer

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