What is a food allergy?

Medically reviewed on February 17, 2022 by Jordan Stachel, M.S., RDN, CPT. To give you technically accurate, evidence-based information, content published on the Everlywell blog is reviewed by credentialed professionals with expertise in medical and bioscience fields.

Food allergies are quite common. Researchers estimate that 32 million people in the United States have food allergies [1]. That includes about 5.6 million children under the age of 18, which averages out to roughly one in 13 children [2].

To the uninitiated, food allergies may seem negligible, but they should be taken seriously. Severe allergic reactions can lead to serious health issues, and they can even be potentially fatal. Often, the best way to handle food allergies is to avoid the allergen, but that can require significant lifestyle changes.

It’s important to understand food allergies as much as possible, for your own health and for the health of everyone around you. Read on to learn more about food allergies and how they work.

What Is a Food Allergy?

A food allergy is a condition that is characterized by a harmful immune response when exposed to certain food components. Your immune system normally protects your body from outer threats. The immune system has built-in processes to differentiate between harmful microbes, like bacteria and viruses, and things that are harmless to your health.

If you have an allergy, your immune system has a little more trouble with that distinction. With a food allergy, your immune system sees specific food proteins as a threat, despite being harmless. The proteins that trigger these reactions are called allergens [3].

Allergens are frequently found in more than one food. For example, if you are allergic to cow’s milk, you are likely allergic to caseins and whey proteins (alpha-lactalbumin and beta-lactoglobulin). These proteins are also present in milk from other mammal species, including goat’s milk and sheep’s milk, so you may likely be allergic to those forms of milk as well [3].

When exposed to a food allergen, your immune system reacts by releasing antibodies known as immunoglobulin E (IgE). To “fight off” the food proteins, IgE releases a chemical called histamine, resulting in many of the physical symptoms associated with food allergies. IgE is not the only component that can cause food allergies, but it is the most common. Food allergies that are not caused by IgE are known as non-IgE-mediated food allergies.

Food Allergy Symptoms

Symptoms of an allergic reaction can vary based on the person and the amount of food that they have been exposed to. Even the smallest amount of exposure can lead to a severe reaction. Allergic reactions can also affect several different parts of the system simultaneously. Symptoms typically develop within minutes of exposure, though some people may experience symptoms a few hours after exposure [4].

The most common symptoms of a food allergy reaction include:

• Hives, itching, eczema
• Itching or tingling sensation in the mouth
• Swelling in the face, lips, throat, or tongue (can also spread to other parts of the body)
• Nasal congestion, wheezing, difficulty breathing
• Digestive issues, including abdominal cramps, diarrhea, vomiting, and nausea
• Fainting, dizziness, lightheadedness [5]

Severe allergic reactions are known as anaphylaxis. Symptoms of anaphylaxis include:

• Tightening and constriction of the airways
• Swelling in the throat or a feeling of something blocking your throat, making it difficult to breathe
• A severe drop in blood pressure leading to shock
• Rapid heartbeat
• Loss of consciousness [5]

Anaphylaxis requires immediate medical treatment. Without treatment, anaphylaxis can potentially lead to a coma or even death [5].

Common Food Allergies

You can be allergic to any food that exists. The “big nine” most common food allergies are:

• Eggs
• Milk
• Peanuts
• Soy
• Wheat
• Shellfish
• Fish
• Tree nuts
• Sesame [6]

If you have a soy allergy, peanut allergy, egg allergy, or seafood allergy you must be especially careful, as these ingredients are commonly found in a wide range of products.

What Causes Food Allergies?

While we know that allergies come from a faulty immune system, the actual cause of that malfunction still requires further research. Food allergies tend to be more common among people whose family members also have food allergies, suggesting that there may be a genetic or hereditary component [7].

Some studies suggest a correlation between environmental factors and food allergies [8]. For example, in some countries where people avoid certain foods, the rates of allergies to that food tend to be higher. Living in a farming environment may actually lower the risk of certain allergic symptoms, like rhinitis and atopic dermatitis. Air pollution may also increase your potential for developing food allergies. Again, these are merely correlations, not causations.

It is possible for people to outgrow food allergies, which is typically more common in infants and toddlers. However, more severe food allergies tend to last the entire life. It is also possible for people to develop food allergies later in life as their body’s immune system changes [7].

Food Allergies, Sensitivities, and Intolerance

Food allergies are frequently confused with food sensitivities and food intolerances. While there may be some overlap, these are three separate conditions that should be treated as such.

Like food allergies, food sensitivities also involve an immune reaction; however, instead of IgE antibodies, IgG antibodies are implicated in food sensitivities. Unlike food allergies, this reaction is much less severe. Symptoms of food sensitivities typically only involve gastrointestinal problems (diarrhea, nausea, abdominal pain, vomiting) and headaches or migraines [9]. If you're wondering whether you may be experiencing food sensitivities, taking an at-home Food Sensitivity Test may be a good place to start.

Food intolerances are characterized by an inability within the gastrointestinal system to process food properly. For example, lactose intolerance is caused by a deficiency in the enzyme lactase, which is required to break down the dairy protein lactose. Symptoms of food intolerance most often involve gas, bloating, stomach pain, and diarrhea [9].

Food sensitivities and food intolerance are serious in their own ways. They can disrupt your quality of life, and the symptoms involved can be painful and uncomfortable. However, they generally aren’t as life-threatening or as severe as a food allergy [9].

Most people with food intolerances or food sensitivities can eat small amounts of the food allergen without experiencing any issues. By comparison, for those with food allergies, even the smallest amount of an allergen will contribute to an allergic reaction every single time [9].

Many people with food sensitivities don’t realize they have them because the symptoms can take a few days to develop. Regardless, if you find yourself suffering from reactions, you may be suffering from food sensitivity. To learn more about potential food sensitivities, consider taking the Everlywell Food Sensitivity Test to find out more.

Treating and Preventing Allergic Reactions

There is no cure for allergies, but as mentioned, it’s possible to grow out of your allergies. For mild allergic reactions, you may be able to manage or reduce symptoms by using over-the-counter or prescribed antihistamines. After exposure to an allergen, antihistamines can help relieve hives or itching.

Severe allergic reactions require a shot of epinephrine and a trip to the hospital. If you have severe food allergies, it’s a good idea to always carry an epinephrine auto-injector with you. Make sure you (and those close to you) know how to safely use the injector and replace it prior to its expiration date.

While it can be hard to pinpoint the exact source of an allergy, testing for it is a great place to start. If you are showing allergic symptoms or an adverse reaction to a particular food, consider doing food allergy testing. This can help you distinguish whether you are suffering from an egg, tree nut, or any other allergen that may be causing you symptoms. The best way to prevent reactions is to avoid foods that have caused a known allergic reaction. Read the labels on all the food products you purchase and know how allergens may appear in the ingredient lists.

When eating out, make your allergies known. If you are planning a trip on a plane, inform the airline of your allergy prior to your flight. They can take the proper precautions to prevent potential exposure via airborne allergens in the cabin.

Food allergies are a serious condition, but with some precautions and a better understanding of their symptoms, you can maintain a happy existence without having to deal with a severe reaction. If you want to learn more, consult your allergist, who can provide you with more information and help you develop steps for managing your allergy.

If you're interested in learning more about your body's reactions to food in ways unrelated to allergies, consider a food sensitivity test.

Related content

Food Sensitivities vs. Food Allergies: How To Determine the Difference

What is the most common food allergy?

References

1. Facts and Statistics. Food Allergy Research & Education. URL. Accessed February 17, 2022.

2. Food Allergies. Centers for Disease Control and Prevention. URL. Accessed February 17, 2022.

3. Allergenic Foods and their Allergens. University of Nebraska-Lincoln. URL. Accessed February 17, 2022.

4. Causes-Food allergy. National Health Service. URL. Accessed February 17, 2022.

5. Food allergy - Symptoms and causes. Mayo Clinic. URL. Accessed February 17, 2022.

6. Common Allergens. Food Allergy Research & Education. URL. Accessed February 17, 2022.

7. Food allergy: Can it develop later in life? Mayo Clinic. URL. Accessed February 17, 2022.

8. Environmental Factors Contribute to the Onset of Food Allergies. Journal of Environmental Science and Public Health. URL. Accessed February 17, 2022.

9. Food allergy, intolerance, or sensitivity: What’s the difference, and why does it matter? Harvard Health. URL. Accessed February 17, 2022.