Food allergies affect about 33 million people in the United States. Having food allergies can feel overwhelming. As one MyFoodAllergyTeam member shared, “I got food allergies at 50 years old, and it is the hardest thing I have dealt with.”

Not all food allergies are the same. Learning about the different types of food allergies can help you spot symptoms, get the right treatment, and manage your condition more effectively. In this guide, we’ll explain the three main categories of food allergy reactions, explaining what causes each type, their symptoms, and how doctors diagnose them. Keep in mind this information is for informational purposes only. If you think you may have a food allergy, talk with your doctor.

1. IgE-Mediated Food Allergies

Immunoglobulin E (IgE)-mediated food allergies are the most common type of food allergy. It can cause a wide range of symptoms that affect the skin, gastrointestinal (GI) tract, respiratory tract, and cardiovascular tract. With IgE-mediated food allergies, your immune system reacts too strongly to certain foods. Symptoms usually appear quickly, within minutes to a few hours after eating.

Here’s how it works: Your body makes a protein called immunoglobulin E. Normally, IgE helps fight things like parasites. But in someone with an IgE-mediated allergy, IgE mistakes specific foods as dangerous. This causes the body to release chemicals called histamines to protect you. Histamines trigger symptoms associated with an allergic reaction, including:

• Hives or skin rash
• Swollen lips, face, or throat
• Wheezing or difficulty breathing
• Nausea, vomiting, or diarrhea
• Dizziness or fainting
• Symptoms of anaphylaxis (a severe and life-threatening reaction)

Major Food Allergens

The most common foods that trigger IgE-mediated food allergens are eggs, fish, milk, peanuts, shellfish, soy, tree nuts, and wheat. Although people can be allergic to other, less common foods as well, these foods cause the most severe allergic reactions:

• Eggs
• Fish
• Milk
• Peanuts
• Shellfish
• Soy
• Tree nuts
• Wheat

Some of these allergies begin in childhood, and in many cases, children outgrow them by the time they reach adulthood. Reactions to these allergens can range from mild symptoms to severe anaphylaxis.

Oral Allergy Syndrome

Oral allergy syndrome (OAS), sometimes known as pollen-food syndrome, is a subtype of IgE-mediated food allergies. OAS often affects people who also have hay fever, or allergic rhinitis. OAS happens because the proteins in certain raw fruits and vegetables are similar to proteins found in pollen, which confuses the immune system and causes a reaction.

Symptoms are usually mild and stay near the mouth area, such as itching or swelling of the lips, tongue, or throat.

Foods that commonly trigger OAS are:

• Fruits, such as apples, pears, peaches, plums, cherries, and melons
• Nuts, including almonds or hazelnuts
• Vegetables, like carrots, celery, and tomatoes

Most people with OAS can eat these foods without trouble once they’re cooked, since the heat changes the protein structure enough to stop the reactions.

2. Non-IgE-Mediated Food Reactions

Non-IgE-mediated food allergies don’t involve IgE antibodies. Unlike IgE-mediated reactions, non-IgE food allergies have chronic (long-term) symptoms and a more delayed onset of symptoms, making it harder to identify the food responsible. Most symptoms of non-IgE-mediated allergies affect the stomach and GI tract, like bloating, diarrhea, and vomiting. In some cases, they may also affect the skin or lungs.

There are a few different conditions that fall under non-IgE-mediated food reactions.

Food Protein-Induced Enterocolitis Syndrome

Food protein-induced syndrome (FPIES) is a serious allergic condition that usually appears in young children just beginning to eat solid foods. FPIES causes ongoing gastrointestinal symptoms such as diarrhea, vomiting, weight loss, and trouble growing. If your child shows any of these symptoms, it's very important to see a doctor right away. The most common food allergens that cause FPIES include:

• Rice
• Milk
• Soy
• Oats
• Chicken
• Fish
• Turkey

FPIES reactions can be severe enough to require hospitalization. Strictly avoiding the trigger foods is necessary to avoid symptoms. The good news is that many children outgrow FPIES by the time they are 3 or 4 years old.

Although FPIES is most common in children, in rare cases it can also appear later in life. One MyFoodAllergyTeam member shared, “I have adult FPIES, which took 28 years to be diagnosed accurately. … I became allergic to peanuts in 1993. In 2019, I turned from vegetarian to vegan, and by the end of that year, I became allergic to 12 other foods.”

Eosinophilic Esophagitis

In eosinophilic esophagitis (EOE), the esophagus — the tube that carries food from your mouth to your stomach — becomes inflamed and narrow, making it hard to swallow hard or dry foods.

You can develop EOE at any age, but the symptoms may look different depending on how old you are. Young children may refuse to eat or have trouble gaining weight, while adults often have trouble swallowing. At any age, people may experience chest pain, heartburn, abdominal pain, and nausea.

Although EOE can sometimes be linked to environmental allergies, food allergies are usually the main cause. Because it’s a chronic illness, treatment is needed for life. Treatments include elimination diets, corticosteroids, and proton pump inhibitors (drugs to reduce the amount of stomach acid produced). In severe cases that do not respond to other treatments, children may be placed on an elemental diet, which replaces all regular food with a special formula containing amino acids, sugars, and oils.

Eosinophilic Gastritis and Gastroenteritis

Eosinophilic gastritis (EG) is another type of non-IgE food allergy. It’s similar to EoE, but instead of affecting the esophagus, it causes inflammation to the stomach. If symptoms affect both the stomach and small intestine, the condition is called eosinophilic gastroenteritis (EGE). Together, EOE, EG, and EGE are known as eosinophilic gastrointestinal diseases (EGID).

In each of these conditions, a type of white blood cell called an eosinophil builds up in different parts of the digestive system, leading to inflammation.

People with eosinophilic gastritis may experience:

• Stomach pain
• Nausea and vomiting
• Diarrhea
• Blood in stool
• Poor appetite and weight loss

Food Protein-Induced Allergic Proctocolitis

Food protein-induced allergic proctocolitis (FPIAP) is a non-IgE-mediated food allergy that mainly affects breastfed infants. It’s often the mildest form of non-IgE food allergies. FPIAP may be difficult to identify since infants usually appear healthy and grow normally, but you may notice fussiness during feeding or see blood and mucus in their stool. Most infants with FPIAP outgrow the condition by the time they are between 1 and 3 years old.

3. Mixed IgE- and Non-IgE-Mediated Food Allergies

It’s also possible to have an allergic reaction that’s both IgE- and non-IgE-mediated. In these cases, you might have some symptoms, like swelling or hives, immediately (IgE-mediated), along with symptoms that appear later (non-IgE-mediated), like skin or GI issues.

How Doctors Diagnose Different Types of Food Allergies

Doctors use different food allergy diagnostic processes depending on the symptoms and the type of allergy suspected.

Common diagnostic tests for food allergies include:

• Oral food challenges — Eating small amounts of suspected food triggers under medical supervision to check for an allergic reaction
• Skin prick tests — Placing small amounts of allergens on the skin to see if a reaction happens
• Blood tests — Measure IgE antibodies to certain foods
• Elimination diets — Removing suspected foods to see if symptoms improve, then adding foods back into your diet one at a time to identify triggers

For non-IgE-mediated allergies, there are no specific tests. Diagnosis will vary depending on the type of non-IGE-mediated allergy, but doctors often recommend elimination diets. They may also use an endoscopy or biopsy to look inside the digestive tract or take tissue samples of the digestive tract (specifically for conditions like EoE).

Food Intolerance vs. Food Allergy: What’s the Difference?

Food allergies and food intolerances are often confused, but they’re very different conditions that require different approaches.

Food allergies involve the immune system and can be life-threatening. With food allergies, even small amounts can cause a negative reaction, so it’s important to completely avoid the trigger food. Symptoms of an allergic reaction often appear quickly.

Food intolerances don’t activate the immune system. They only affect the digestive system. Food intolerances often happen because your body doesn’t have enough of a specific enzyme required to break down certain foods or because of a sensitivity to a food additive. Reactions usually happen after eating larger amounts, and many people can tolerate small amounts. Common symptoms of food intolerances are mostly digestive, such as bloating, gas, and diarrhea. Unlike allergies, food intolerances are usually not life-threatening.

When To See a Doctor

If you notice symptoms of food allergies after eating certain foods, talk to your healthcare provider. Your doctor will start by asking you questions about your medical history, symptoms, and current diet to help confirm a diagnosis.

Understanding the type of food allergy you have helps you and your healthcare team make the best possible management plan. With the right diagnosis and care, people with all types of food allergies can live healthy, active lives while still staying safe and enjoying a variety of foods.

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