How to Tell if I Have Food Allergy

Food allergy symptoms occur when the immune system mistakenly handles proteins in some foods as a danger to your body. It releases several chemicals during this process, causing an allergic reaction. If you have a food allergy, your immune system can see proteins in some food as an invader or allergen. Your immune system over-reacts by producing antibodies called Immunoglobulin E (IgE). These antibodies travel to cells that release chemical compounds such as histamine and cause allergic reactions. However, these reactions can range from annoying sneezing and itching to life-threatening reactions “anaphylaxis”.

Symptoms of Food Allergy

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Symptoms of food allergies, or food intolerance, always develop within a few seconds or minutes of consuming that food. Signs and symptoms can vary from mild to severe and affect each person differently. Not every person can experience all potential symptoms, however, each reaction can be slightly different. The symptoms may include the gastrointestinal tract, skin, or respiratory tract. Common symptoms of food allergies include: (1, 2, 3, 4)

  • tingling or itching in the mouth
  • a raised itchy red rash (hives)
  • swelling of the throat, lips, mouth
  • difficulty swallowing
  • wheezing, or shortness of breath
  • feeling dizzy and lightheaded,
  • feeling sick (nausea) or vomiting
  • abdominal pain or diarrhoea
  • hay fever, sneezing, or itchy eyes

Symptoms of anaphylaxis

Anaphylaxis is a life-threatening allergic reaction that triggers the immune system to release a storm of chemicals. In addition, it can cause your blood pressure to drop and your airways to close, preventing you from breathing. Symptoms of a severe allergic reaction (anaphylaxis) may be rapid or get worse quickly. Signs and symptoms may include: (5, 6, 7, 8, 9)

  • breathing difficulties
  • swollen tongue
  • swollen throat,
  • tightness in the chest
  • trouble speaking or nausea
  • feeling dizzy or faint,
  • skin itchy or rashes over all body
  • rapid drop in blood pressure
  • fast heartbeat or collapse

Anaphylaxis is an emergency medical condition. Without immediate treatment, it can be life-threatening. If you suspect yourself or someone you know is having anaphylaxis, call emergency and ask for an ambulance as soon as possible.

Food Allergy Triggers

If you have a food allergy, the IgE antibodies can feel it and signal your immune system to release a chemical called histamine, and other chemicals into your bloodstream. The most popular allergenic foods account for around 90% of all food allergies. (10, 11)

Food allergy among adults

Most adults who are allergic to food have had it since they were children. Adults will often miss an allergic reaction to food because symptoms like vomiting and diarrhea are mistaken on food poisoning. In adults, certain proteins cause food allergies in:

  • eggs
  • fish
  • shellfish
  • milk
  • peanuts
  • hazelnuts
  • walnuts
  • cashews
  • pistachios
  • soybeans
  • pecans
  • wheat

Food allergy in children

According to the Johns Hopkins Medicine, food allergy affects about 5% of children under the age of five. Between 1997 and 2007, the number of children under the age of 18 who had food allergies increased by 18%. In children, proteins usually cause food allergies include: (12, 13)

  • Eggs
  • Peanuts
  • Tree nuts,
  • Soy
  • Cow’s milk
  • Wheat

Some seeds, including sesame and mustard seed, are also popular triggers and are considered being a significant allergen in some countries. If you think you or your child have a food allergy, make an appointment with your doctor. The doctor will ask about their food reactions. Your doctor needs you to know:

  • what symptoms do your child experience after ingestion of food?
  • how long does it take for the reaction to begin?
  • how long did the symptoms last?
  • which food triggered the reaction to begin with?
  • was the food cooked or raw?
  • how severe were the symptoms?
  • is it the first time these signs have occurred?
  • how much did the symptoms occur?
  • what food did your child eat and how much of it?
  • is there a family history of allergies?
  • was your child breastfed or bottle-fed?

If your child is allergic to food, the doctor will also check the weight and height of your child to make sure your child is growing at the estimated pace. If your doctor suspects a food allergy, you or your child might be referred to an allergy clinic for testing. The tests required can vary depending on the type of allergy:

Skin-prick testing

In this skin-prick test, they mount some drops of standardized food extracts on the arm. The allergist will pierce your skin with a small lancet, which enables the allergen to come into contact with the cells of your immune system. (14, 15)

Blood test

An alternative to a skin-prick test is a blood test that tests the amount of allergic antibodies in the blood. The doctor will take your blood sample and check for allergies. It’s more costly than the other tests. (15)

Challenge tests

Often challenge tests are for food allergies. In this test, patients ingest or inhale a small amount of allergens under close surveillance of an allergist. Do not try this test at home! (15)

Food Allergy Treatment

The standard approach to food allergy treatment is that to avoid the food that causes the reactions. Oral immunotherapy is another relatively recent and experimental method of treating food allergies. This may involve gradually rising the amount of an allergen given to the individual in order to raise the threshold that causes a reaction. Oral immunotherapy is not effective for all food allergies, although the Food and Drug Administration (FDA) has approved Palforzia, a treatment for peanut allergy. Elimination may involve not to swallow, inhale, touch, or eat foods containing traces of it. Cutlery, crockery, cooking surfaces, and chopping boards should also be allergen-free. However, there are medicine for emergencies, such as antihistamine and adrenaline, which can ease symptoms of food allergies. (16, 17, 18, 19)


Antihistamines are used to treat mild to moderate allergic reactions. Many antihistamines are available over the counter. Some antihistamines are not appropriate for children. Ask your doctor what forms of antihistamines might be acceptable for you and your child. (20, 21, 22)

Epinephrine (adrenaline)

Epinephrine (adrenaline) is to treat serious allergic reactions (anaphylaxis). It acts by narrowing the blood vessels to withstand the effects of low blood pressure and widening the airways to help relieve breathing difficulties. In case of emergency, they will give you an adrenaline auto-injector if you or your child are at risk of anaphylaxis or have had a prior episode of anaphylaxis. (23, 24, 25)

Risk Factors

Any food can induce an allergic reaction, but in reality, only a few foods responsible for the vast majority of food allergies. The allergies that people encounter are because of dietary patterns, age, and family history. (26, 27)

Family history: If you have a history of asthma, eczema, hives, or allergies, such as hay fever in your family, then you are at a higher risk of developing food allergies.

Age: Children, especially toddlers and infants, are more prone to food allergies. When the children grow, their digestive system matures, and their body is less likely to absorb allergens. However, allergies to nuts and shellfish are more likely to be permanent.

Other allergic conditions: Asthma and food allergies are frequently found together. When they do, the symptoms of both food allergies and asthma are more likely to be severe.

Gut bacteria: According to some studies, people who have nut or seasonal allergies have altered gut bacteria. They have higher levels of Bacteroidales and lower levels of Clostridiales. Scientists are attempting to determine whether manipulating gut bacteria will aid in prevention of allergies.

Exercise-induced food allergy

Some people may experience itching and lightheadedness shortly after exercising if they consume certain foods. In severe cases, hives or anaphylaxis may occur. Avoiding certain foods and not eating for a couple of hours before exercising can help prevent this dilemma.

Asthma: Exercise also causes an asthma attack in people with asthma, but some people only have asthma when they exercise. Exercise can trigger or exacerbate asthma because rapid breathing can cool and dry the airways, and when the airways warm up again, they get narrow. Because the chest is constricting, people can wheeze, cough, and have trouble breathing. (28)

Anaphylactic reactions: Vigorous exercise can sometimes trigger a widespread, potentially fatal allergic (anaphylaxis) reaction. This reaction occurs only in some people if they eat a specific food such as wheat and shrimp before exercise. Breathing becomes difficult, and blood pressure drops, causing dizziness and collapse. An anaphylactic reaction is potentially fatal. (29, 30)

Exercise-induced symptoms, such as asthma or an anaphylactic reaction, typically appear after 5 to 10 minutes of intense exercise. Symptoms can also appear after the completion of an exercise.

Allergy vs. food intolerance

Some symptoms of food intolerance and food allergy are identical. However, the variations are important to know. Eating food that you are intolerant to will make you feel awful. If you have a food allergy, the body’s reaction to the food may be fatal. A food intolerance reaction occurs in the digestive system. It happens when you cannot properly break down the food. This may be because of the lack of enzyme, exposure to food additives, or reactions to naturally occurring chemicals in foods. Sometimes, people can consume small quantities of these foods, causing no problems. (31, 32, 33)

Common conditions

Here are some common conditions that are misunderstood as a food allergy include:

A lack of enzymes: Any enzymes needed for the digestion of certain foods may lack in your body. Inadequate levels of the enzyme lactase, for example, impair the ability to digest lactose, the primary sugar in dairy products. Lactose intolerance can lead to bloating, cramping, diarrhoea, and gas.

Food poisoning: Food poisoning may often cause an allergic reaction. Bacteria in spoiled tuna and other fish may also produce a toxin that causes adverse reactions.

Sensitivity to food additives: Certain food additives cause digestive reactions and other symptoms in some people. Sulfites, for example, which are used to preserve dried fruit, tinned food, and wine, can cause asthma attacks on people who are sensitive to them.

Histamine toxicity: Certain fish that are not adequately refrigerated and contain high levels of bacteria can often contain high levels of histamine, which causes symptoms similar to food allergies. This is considered histamine toxicity or scombroid poisoning rather than an allergic reaction.

Celiac disease: Celiac disease is a gluten allergy. It does not cause anaphylaxis. It is an immune system response, just like a food allergy, but it is a unique reaction that is more complex than a simple food allergy. Gluten, a protein found in wheat, pasta, cookies, and many other foods, may cause this digestive disorder.

If you have celiac disease and consume gluten-containing foods, an immune response arises that damages the surface of your small intestine, resulting in an inability to absorb certain nutrients.

Pollen-food allergy syndrome

Pollen-food syndrome (PFS) occurs when the body reacts to proteins present in plant-based foods that are close to pollen. It is most common in people who have hay fever in the spring. It’s also known as Oral Allergy Syndrome (OAS), and it’s the most common form of food allergy among adults. The table below lists the fresh fruits, vegetables, nuts, and spices that can cause pollen-food allergy syndrome in people allergic to various pollens. (34, 35, 36, 37)

If you are allergic to:Birch pollenRagweed pollenMugwort pollenGrasses
You may also react to:Almond
Raw potatoes
Bell pepper
Black pepper
Caraway seed
White potato
If you are allergic to pollens, your body may react to these spices, fruits, and vegetables.


A food allergy is an immune system response. It occurs when the body mistakes an ingredient in food as a hazard by your immune system. Your body releases a range of chemicals that give rise to an allergic reaction. Eggs, milk, and peanuts are the most common food allergies in children. The symptoms can be mild to extreme. There is no conventional remedy for food allergies, but oral immunotherapy provides hope and allows patients to treat symptoms as they occur. People can avoid allergic reactions by avoiding products containing the allergen. Before introducing allergenic foods to your child, consult with your doctor about the best time to do so.


  1. Symptoms of food allergy. NHS.
  2. Anaphylaxis. Mayo Clinic Staff.
  3. Food allergies. Cleveland Clinic.
  4. Allergens food. The Johns Hopkins University.
  5. Food allergy testing. MedlinePlus.
  6. FDA approves the first drug for treatment of peanut allergy for children. U.S. Food and Drug Administration.
  7. Allergy relief: Antihistamines vs. Decongestants. webMD.
  8. Epinephrine Injection. MedlinePlus.
  9. Chen, J.Y.F., Quirt, J. & Lee, K.J. Proposed a new mechanism for food and exercise induced anaphylaxis based on case studiesAll Asth Clin Immun 9, 11 (2013).
  10. Food allergy vs. food intolerance: What’s the difference? Mayo Clinic Staff.
  11. Food allergy. Mayo Clinic Staff.
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Naeem Durrani BSc
I am a retired pharmacist, nutrition expert, journalist, and more. My interests include medical research, and the scientific evidence around effective wellness practices, which empower people to transform their lives.

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