Food Allergies

What is Food Allergy?

Food allergies in children and adults are common. According to The Centers for Disease Control and Prevention (Opens in a new window) (Opens in a new window) (Opens in a new window), in the U.S., 32 million people have food allergies, that’s about one in four children and one in three adults. Globally, food allergies affect 220 million people (Opens in a new window) (Opens in a new window) (Opens in a new window). 

Rates of Food Allergy by Country (Opens in a new window) (Opens in a new window) (Opens in a new window)

Most food allergies develop in babies, but it is possible to develop food allergies later in life. Children may outgrow allergies to milk and egg, but allergies to peanuts or tree nuts are usually lifelong.

Types of Food Allergies

There are four main types of food allergies.

1. Immunoglobulin E-mediated (IgE-mediated) – This is the most common type of food allergy, and the one described on this page. 

2. Non-IgE-mediated – This type of food allergy usually involves the gut or digestive tract. Examples of non-IgE-mediated food allergy include eosinophilic esophagitis (EoE), food protein-induced enterocolitis syndrome (FPIES) and allergic proctocolitis (Opens in a new window) (Opens in a new window) (Opens in a new window).

3. Mixed IgE-mediated and non-IgE-mediated – This is a type of immune-mediated adverse food reaction that can include eosinophilic gastrointestinal disorders and skin conditions like atopic dermatitis (eczema).

4. Hypersensitivity – This type of food allergy is associated with celiac disease and similar disorders.

Food Allergy Causes

Food allergy is an immune-system reaction. When the immune system is not working right, it thinks a harmless food protein is a dangerous invader. To protect your body, the immune system produces the immunoglobulin E (IgE) antibody. IgE triggers cells to release histamine and other chemicals. These substances cause symptoms of an allergic reaction. 

Common Food Allergens

According to the Food and Drug Administration (Opens in a new window) (Opens in a new window) (Opens in a new window), more than 160 foods can cause food allergies in people who are food sensitive. These are the nine most common foods (Opens in a new window) (Opens in a new window) (Opens in a new window) that cause food allergy reactions in children and adults. They account for about 90% of food allergies and serious reactions.

1. Dairy
2. Egg
3. Fish (such as bass, cod flounder)
4. Peanuts
5. Shellfish (clams, crab, lobster, shrimp and scallops)
6. Tree nuts (almond, Brazil nut, cashew, hazelnut, macadamia, pecan, pine nut, pistachio walnut)
7. Wheat
8. Sesame 
9. Soybeans

Signs and Symptoms

Food allergies can be inherited. You have an increased risk of developing food allergies if your family has:

• Asthma
• Eczema
• Hives
• Allergies (hay fever)

If you have an allergy to one food, you may be at risk for developing other food allergies. 

Allergic reactions to food usually within 30 minutes after eating, and almost always within 2 hours. Food allergy symptoms may be different for each child and adult. Symptoms of food allergy can involve the heart, lungs and nose, mouth, stomach or skin.

The most common food allergy symptoms can include: 

• Dizziness, lightheadedness, or fainting
• Hives 
• Itching or tingling in the mouth, face, tongue or lips
• Stomach pain, diarrhea, nausea or vomiting
• Swelling of the lips, face, tongue or throat
• Wheezing or trouble breathing

Other food allergy symptoms include:

• Low blood pressure
• Shock
• Runny nose, coughing or sneezing
• Flushing (redness)
• Swelling in other parts of the body

Severe reactions can affect the whole body and be life-threatening. This is called anaphylaxis. It can cause loss of consciousness and stopped breathing. Call 911 immediately if you suspect this serious reaction.

Conditions Related to Food Allergies

Food Intolerance

Some people confuse food intolerance with food allergies. Food intolerance is a not the same as a food allergy because it is not caused by the immune system. In general, food intolerance is not life-threatening. It is caused by not having the right enzymes to fully digest a food. A good example is dairy or lactose intolerance. If you are lactose intolerant, your body can’t completely digest the sugar (lactose) in milk or milk products. This causes gas, bloating or diarrhea soon after eating or drinking it. 

Food intolerance also is common. Experts estimate that about 20% of the population has this condition. Learn more about the difference between food allergy and food intolerance 

Oral Allergy Syndrome

In a small group of people who have pollen allergies, eating certain raw fruits and vegetables can cause a reaction that may seem like a food allergy. This reaction is called oral allergy syndrome or pollen-food allergy syndrome. It is an example of local (instead of systemic) IgE-mediated food allergy. Some raw foods have proteins that are similar to pollen proteins. The raw form of these foods can cause symptoms like itching and swelling of the mouth, lip, tongue and throat. For example, some people who are allergic to Timothy grass may react when eating cantaloupe or honeydew melons.

Oral allergy syndrome reactions can be mild to severe. 

Diagnosis

Food allergies need to be diagnosed by a doctor. Your primary doctor may refer you to an allergist who is a food allergy specialist. 

To diagnose food allergies, the allergist will review your medical history and do a physical exam. The doctor will ask questions about food-related reactions, such as:  

• What food seems to cause symptoms?
• How much of the food did you eat?
• What symptoms did you have after eating the food?
• How long after eating did you have symptoms of an allergic reaction?
• Do you have symptoms every time you eat the food?
• Did you have symptoms when eating other foods?
• Do you have family members who have food allergies?
• What foods are your family members allergic to?

Depending upon the results of the evaluation, your doctor may ask you to keep a food diary to record:

• The foods you eat
• When you eat them
• When a reaction occurs
• What the reaction was
• How you treated the reaction

Common Tests for Food Allergies

Testing for food allergies can include allergy skin testing, bloodwork and the oral food challenge.

Allergy Skin Testing

This is a skin prick test, which can identify your reaction to a specific food. During the test, a small amount of the food allergen is placed on the skin (usually on the back). Then the skin is pricked. Allergy is indicated by a bump and redness developing where the skin was pricked. This positive reaction is not enough to confirm an allergy to the food.  

Allergy Blood Test

A simple blood test measures the amount of allergy-related antibody, immunoglobulin E (IgE) in the blood. This test can indicate a food allergy, but it can’t confirm a food allergy or identify how severe the allergy is.

Oral Food Challenge

The most accurate test for diagnosing food allergies is the oral food challenge. This test was developed in the 1970s by National Jewish Health pediatrician and expert on childhood nutritional disorders Charles May, MD (Opens in a new window) (Opens in a new window) (Opens in a new window), and his colleagues. The oral food challenge remains the gold standard way to diagnose food allergies.

During this test, very small amounts of a food is eaten slowly, in gradually increasing amounts.  Food challenges are done under medical supervision and are considered very safe. There is some risk of a severe allergic reaction. Because of that risk, food challenges should only be performed in a medical setting. National Jewish Health has all the necessary medications, equipment and medical staff who are experienced in treating severe allergic reactions (anaphylaxis) in case it happens.

Benefits of Food Challenge Testing

1. Determine if a wrong food is suspected of causing symptoms 

It’s important to know which food is the allergen so you are not eliminating the wrong foods from your diet. Knowing the exact food(s) you are allergic to can help prevent future reactions. 

Sometimes the food responsible for the reaction is not apparent from skin or blood testing. For example, a patient may have a positive skin test to several suspected foods. Food challenges may be necessary to determine which, if any, of the foods is the allergen. 

It is possible that food can be contaminated other allergens and lead to wrong conclusions, for example:

• Reacting to a French fry cooked in peanut oil might cause you to suspect a peanut allergy. The actual cause of the reaction may be the fish that was fried in the same oil. 

• Sometimes a nonfood contaminant can cause the reaction. Latex proteins can be deposited on foods by people wearing latex gloves. 

• Dust mites can contaminate baked goods and cause a reaction.

• Reacting to peanuts at a baseball game may not mean you are allergic to them. Studies show that only a very small amount of peanut protein can become airborne or aerosolized, and it is often too small to cause a reaction and it does not travel far. Other causes of symptoms may be dust, grass or smoke sensitivities.  

2. Prove that a food is NOT the cause of food allergy symptoms 

Occasionally having a broad range of blood tests for food allergies can give multiple false positive results. This leads to unnecessarily restrictive diets. The food challenge is specific to one food at a time. This means there are no multiple variables that cause false positive results. There are times when what seems like an allergic reaction to a food is actually brought on by other things like medicines, toxins, parasites, breathing in allergens, touching allergens, viral illness, exercise or panic.

3. Verify if you have outgrown a food allergy 

Many children who are born allergic to milk, egg, wheat or soy outgrow these allergies when they are 3 to 6-years old. About 20% of children will outgrow a peanut allergy and about 10% outgrow a tree nut allergy. A carefully performed food challenge can safely document when the food can be returned to the diet. It also can show if there has been a drastic reduction in significant reactions to the food. Food allergies that develop in adults are most likely lifelong allergies.

4. Determine how much of a food allergen can cause a life-threatening reaction

Some patients and families become concerned that even a tiny amount of a food might cause a life-threatening reaction. These concerns can prevent participation in normal activities and lead to social isolation. When you know your level of sensitivity, you don’t need to avoid all activities. Some patients are found to be more sensitive than they previously suspected. When this happens, it is important to strictly avoid the food. It is also vital to be completely prepared to treat a severe reaction. 

Treatment

There is currently no cure for food allergy. Treating food allergies in adults and children is largely about management. Managing food allergies includes avoiding and reducing exposure to food allergens, being prepared for allergic reactions and taking medicine as prescribed by your doctor. 

Avoid Food Allergy Reactions

An important part of managing your food allergies is avoiding foods that cause reactions. Follow these tips to reduce the risk of accidentally eating a food allergen.

• Know the foods you are allergic to and avoid them.
• Inform people at work, school and home about your food allergy. 
• Your doctor may provide a Food Allergy & Anaphylaxis Emergency Action Plan (Opens in a new window) (Opens in a new window) (Opens in a new window). This plan describes how to treat different types of reactions. Follow your treatment plan.
• Know the medicines your doctor has prescribed to treat food allergy reactions. Carry them at all times.

Reduce Exposure to Food Allergens

The best way to prevent an allergic reaction is to remove exposure to the specific food allergen(s). 

• Know the different names of foods to which you are allergic. For example, casein and whey are both milk products.
• Read labels carefully to identify foods in packages. Manufacturers can change ingredients at any time. Read labels every time you shop.
• Ask about ingredients in food served outside your home. 
• Educate your child’s caregivers about their food allergies.
• Encourage children with food allergies not to eat food given to them by anyone.

Be Ready to Treat Allergic Reactions

It is not always easy for children or adults to avoid food that can trigger a reaction. You need to always be prepared to recognize and treat a reaction. 

Antihistamines can help ease mild symptoms when you accidental eat a food allergen. These drugs can’t prevent a life-threatening reaction (anaphylaxis). The first line and only treatment for anaphylaxis is epinephrine, which is used an auto-injector.  

• Understand allergy medications and know when and how to use them.
• Carry an epinephrine auto-injector (like EpiPen®)
• Carry an oral antihistamine (such as cetirizine or Zyrtec®), preferably in liquid or fast-melt forms as prescribed for emergencies.

Learn more about your food allergies and how to avoid foods you are allergic to by talking with your doctor. Another reliable resource is Food Allergy Research & Education (FARE) (Opens in a new window) (Opens in a new window). National Jewish Health is a FARE Clinical Network Center of Distinction (Opens in a new window) (Opens in a new window).

Medications

For many patients, the best food allergy treatment option is still avoidance, but there are medications to consider. It can be helpful to review the options before your next clinic visit. At that appointment, ask questions so that you and your doctor can decide what is the best treatment for your child. Treatments can be reevaluated later. None of the medication options below are required for food allergies.

Oral Immunotherapy with PALFORZIA®

Oral immunotherapy (OIT) is a treatment that gives a small and increasing amount of a food allergen over a period of time. The goal is to eventually reduce the amount of the allergen that triggers an allergic reaction.  It is not a cure for food allergy. OIT can lessen the severity of a life-threatening allergic reaction.  

PALFORZIA is an OIT product made from peanuts. It was approved by the U.S. Food and Drug Administration (FDA) in 2020 to treat peanut allergy. The initial dose may be given to children aged 4 to 17 years old. Up-dosing and maintenance doses may be given to those 4 years of age and older. 

With this treatment, the child with a peanut allergy eats a small amount of peanut every day at home. Slowly the amount is increased every few weeks. Eventually it is increased to the amount of peanut they can tolerate without triggering a reaction. PALFORZIA is not a cure for peanut allergy. It is not an emergency treatment for accidental exposure that causes an allergic reaction.

At home, the contents of the Palforzia capsules are mixed into food (like pudding or yogurt) and eaten every day. It takes six months or longer to reach the maintenance dose. This is equal to a single peanut. You must continue to take the medicine every day to maintain desensitization. You also must follow a strict peanut-free diet while taking Palforzia.

During clinical research, most recipients receiving this treatment had no more than mild allergic symptoms after six months. Side effects like nausea or vomiting are possible. Because you are eating something that you are allergic to, there is a risk for anaphylaxis. Read more about the research on the FDA website (Opens in a new window) (Opens in a new window). 

Xolair® Injection

In February 2024, the FDA approved Xolair (omalizumab) injection as a treatment for food allergy in adults and children 1 year and older. Xolair reduces allergic reactions (including anaphylaxis) from accidental exposure to food allergens. 

This injection is not approved for immediate emergency treatment of allergic reactions including anaphylaxis. It is rare, but some patients can have anaphylaxis to Xolair. During clinical trials, this medicine was safe and effective for most adults and children with food allergies, while also avoiding their known allergens. Xolair was already approved to treat other allergic conditions like asthma and chronic hives in different age groups. 

See a Specialist

It’s important to be evaluated by a specialist if you, your child or a loved one:

• Has symptoms of a food allergy
• Has had any type of reaction to eating a food
• Has a family history of allergy, eczema or previous food reactions
• Would like strategies to help prevent food allergies from developing in a baby  

At National Jewish Health in Denver, Colorado, we have one of the nation’s leading food allergy treatment programs. Learn more about our program or use the button below to make an appointment.