What Are Food Allergies?

A food allergy develops when your body’s immune system responds abnormally to a particular food. Foods like shellfish, peanuts, and eggs commonly trigger this reaction, ranging from mild to severe or life-threatening.

A food allergy differs from food intolerance, which means your body has difficulty properly digesting food, resulting in mild digestive issues.

This article discusses the symptoms, causes, diagnosis, and treatment of food allergies.

A toddler eating in his highchair

Catherine Delahaye / Getty Images

Types of Food Allergies

Many different types of foods can cause food allergies, but some are more common than others. Foods that account for the most allergic reactions in the United States include:

  • Milk
  • Eggs
  • Fish (bass, flounder, or cod)
  • Shellfish (crab, lobster, and shrimp)
  • Tree nuts (almonds, walnuts, or pecans)
  • Peanuts
  • Wheat
  • Soy
  • Sesame (often found in hummus or tahini)

In adults, fish, shellfish, peanuts, and tree nuts prompt the most allergic reactions. Children tend to experience more food allergic reactions with eggs, milk, peanuts, tree nuts, soy, and wheat.

Symptoms of a Food Allergy

An allergic reaction to a specific type of food can look slightly different for everyone. The reaction can be mild or severe and may affect the skin or the respiratory system. This might include some or all of the following symptoms:

  • Itching or swelling in and around the mouth
  • Stomach pain or cramping
  • Vomiting or diarrhea
  • Hives (raised welts), swelling, or an itchy, bumpy rash
  • Feeling of tightness in the throat 
  • Difficulty breathing
  • Sudden drop in blood pressure

These symptoms can appear a few minutes to hours after ingesting the food.

When Do Food Allergies Start?

There are millions of people living with food allergies. It’s estimated that up to 6% of children and 4% of adults have them. 

Food allergies most commonly develop in infancy and childhood, but they can appear at any age. It’s also possible to develop a food allergy to a food even after having eaten that food for years without an issue.

Food allergies affect roughly 1 in 13 children and 1 in 10 adults in the United States.

What Causes Sudden Food Allergies?

Biological, environmental, and genetic factors cause food allergies.

Researchers are still looking into why some adults experience sudden onset food allergies; these are an allergic reaction to a food they've previously eaten without any issues. One theory is that a sudden or severe life-changing event might play a key role, including:

  • Exposure to a virus that alters the body's normal immune system response
  • Being exposed to a broader range of allergens
  • Experiencing hormonal changes
  • Practicing a hygiene routine that suppresses immune system development

How Do You Know If You Have a Food Allergy?

Each person will experience a food allergic reaction differently. But in general, you'll notice symptoms that range from mild to severe that usually begin within two hours of eating a trigger food. These symptoms typically affect the airways, skin, or stomach.

Testing for Food Allergies

If you're experiencing an allergic reaction to food for the first time and aren't sure which food triggered this response, you can test for it.

At Home

Healthcare providers typically recommend keeping a food and symptom diary at home to help determine a diagnosis. This would include recording the foods you've eaten, the timing, and any symptoms you've experienced for about a week to get an accurate reading.

At-home kits that screen for food allergies are also available, but doing homework before using one is important. With potential concerns about their accuracy, it's best to check with a healthcare provider to get a correct diagnosis.

With a Healthcare Provider

If you suspect you might have a food allergy, make an appointment with a healthcare provider. They will ask questions about your medical history and symptoms, including the types of foods and how much you ate when the reaction appeared, when the symptoms developed, which symptoms you experienced, and how long they lasted.

From there, the following tests may be ordered to help determine whether there are food-specific immunoglobulin E (IgE) antibodies present in your system:

  • A skin prick test involves poking the skin with a needle and provides quick results.
  • A blood test involves drawing blood to measure the antibody amount, with results in a week.

In some cases, the healthcare provider may recommend an oral food challenge to diagnose a potential food allergy. This process includes ingesting a small amount of the suspected food under strict medical supervision to observe whether or not a reaction occurs. Oral food challenges are more likely to be recommended when the medical history or blood test results are unclear.

Treating Food Allergy Symptoms

Food allergy treatment depends on factors like the severity of your symptoms and your overall health. For example:

  • An over-the-counter (OTC) oral antihistamine might be recommended for mild food allergies that cause sneezing, a runny nose, or itchy skin.
  • Prescription medications like injectable drugs used to treat anaphylaxis might be prescribed for more moderate to severe food allergies.
  • Lifestyle tweaks will also be suggested, like avoiding the allergen and preventing a reaction.

Severe Food Allergy Reaction: What Do You Do?

A mild food allergy symptom may involve discomfort in one or more body areas. But a severe reaction will have serious symptoms that might include shortness of breath, tightness in the throat, widespread hives, swelling of the tongue or lips, dizziness, or ongoing vomiting. 

When this happens, it’s important to move quickly, as severe food allergy reactions can become life-threatening. Experts recommend the following steps:

  • Use epinephrine (also known as an EpiPen) if prescribed.
  • Call 911 and request an ambulance for a severe food allergy reaction.
  • Get medical treatment at the emergency room or urgent care, even if your symptoms appear to be resolving.

Signs of Anaphylaxis

Anaphylaxis is a potentially life-threatening allergic reaction that occurs within minutes to hours of ingesting a trigger substance and requires immediate medical attention. If you notice any of the following signs, stop eating the food and seek emergency medical attention right away:

  • Trouble breathing
  • Low blood pressure
  • Shock
  • Swelling of the throat

Can You Prevent Food Allergies?

Unfortunately, there is currently no cure available for food allergies. The best way to prevent an allergic reaction is to avoid the food that causes the issue. Once a healthcare provider has helped you determine which food triggers this response, you should altogether remove them from your diet.

Living With Food Allergies

Living with a food allergy can feel frustrating, especially when constantly worrying about avoiding common foods. Experts recommend the following tips to help you cope and bring some ease to your experience:

  • Be prepared for accidental exposure by carrying a supply of your medication if needed and wearing a medical alert bracelet.
  • Double-check labels whenever you buy a food product, and ask questions about the menu when dining out.
  • Consider at-home remedies like sipping ginger tea and taking an OTC antihistamine for minor uncomfortable food allergy symptoms.


A food allergy develops when your body responds abnormally to certain foods. Common types of food allergies include shellfish, peanuts, and eggs. While many symptoms from a food allergic reaction are mild and may affect the skin or digestive system, some may be severe and even life-threatening.

A healthcare provider can help diagnose a potential food allergy by using a blood test and evaluating your symptoms. Recommended treatment options include OTC antihistamines or prescription medication to manage an attack and avoid the food altogether.

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Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Cristina Mutchler
Cristina Mutchler is an award-winning journalist with more than a decade of experience in national media, specializing in health and wellness content.