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Food Allergy


Disease: Food Allergy Food Allergy
Category: Allergies

Disease Definition:

When an immune system reaction occurs soon after eating a certain food, it means that the person has a food allergy. Digestive problems, hives or swollen airways are some of the signs and symptoms that could be triggered after eating only a tiny amount of the allergy-causing food. In some cases, severe problems, or even a life-threatening reaction known as anaphylaxis could be caused by food allergy.


An estimated 6 to 8% of children under the age of 3 and about 4% of adults are affected by food allergy. Food allergy has no cure; however, some children could outgrow their food allergy as they get older. Food intolerance, which is a common reaction, could easily be confused with food allergy. Food intolerance is a less serious condition and doesn't involve the immune system, despite the fact that it could be bothersome.


Work Group:

Symptoms, Causes


Although uncomfortable, in some cases, an allergic reaction to a particular food may not be severe. In other cases, it could be very frightening and even life-threatening. Usually within a few minutes to an hour after eating the offending food, the symptoms of food allergy start appearing. These are some of the most common signs and symptoms of food allergy:


  • Nausea, vomiting, abdominal pain or diarrhea
  • Tingling in the mouth
  • Swelling of the lips, throat, tongue or other parts of the body
  • Lightheadedness, dizziness or fainting
  • Itching, eczema or hives
  • Trouble breathing, wheezing or nasal congestion



A food allergy in some cases could trigger an anaphylaxis, which is a severe allergic reaction. Anaphylaxis could cause life-threatening symptoms, some of which are:


  • Rapid pulse
  • Constriction and tightening of airways
  • Shock, in addition to a severe drop in blood pressure
  • Loss of consciousness, lightheadedness or dizziness
  • A swollen throat or a lump in the person's throat, which could make breathing difficult.


Because anaphylaxis could cause a coma or death when left untreated, emergency treatment is vital.



In some cases, people have an allergic reaction to a food, which is triggered by exercise. A person with an exercise-induced food allergy could feel itchy and lightheaded, as the body is stimulated by exercise. Hives, anaphylaxis or other reactions could be caused in some severe cases. In order to help prevent this problem, the person shouldn't eat for a couple of hours before exercising and avoid certain foods.



Certain nuts and spices and fresh fruits and vegetables could trigger an allergic reaction in many people who have hay fever, which causes the mouth to itch or tingle. Also called oral allergy syndrome, pollen-food allergy in some people could cause swelling of the throat or anaphylaxis. This is an example of cross-reactivity. Because the proteins in fruits and vegetables are similar to those allergy-causing proteins that are found in certain pollens, they cause a reaction. For instance, a person may react to apples in case they're allergic to birch pollen, and they may also react to melons in case they're allergic to ragweed. In order to help avoid this reaction, the fruits and vegetables could be cooked. Cross-reactive oral allergy symptoms are not caused by most cooked fruits and vegetables.


These are the common cross-reactivity between pollens and fruits and vegetables:


  • In case someone's allergic to birch pollen, they may also react to celery, pears, peaches, raw potatoes, carrots, hazelnut and apples.
  • In case someone's allergic to grasses, they may also have a reaction to tomatoes and kiwis.
  • If someone's allergic to mugwort pollen, they may also have a reaction to celery, carrots, kiwi fruit, peanuts, apples and certain spices, such as anise seeds, fennel seeds, coriander, caraway seeds and parsley.
  • If someone's allergic to ragweed pollen, they may also react to tomatoes, bananas and melons, including watermelon, cantaloupe and honeydew.


In case a person experiences food allergy symptoms shortly after eating, they should see a doctor or an allergist. A person should see a doctor when the allergic reaction is occurring if it is possible, because it will help the doctor in making a diagnosis. If a person develops any signs and symptoms of anaphylaxis they should seek emergency treatment. These signs and symptoms include:


  • Rapid pulse
  • Lightheadedness or dizziness
  • Constriction of airways that makes it difficult to breathe
  • Shock, along with a severe drop in blood pressure.


When a true food allergy occurs, the affected person's immune system mistakenly identifies a specific food or a substance in food as a harmful substance, and triggers cells to release antibodies called immunoglobulin E (IgE) antibodies, in order to fight the culprit food or food substance, also known as the allergen. The IgE antibodies will sense the next time that person eats even the smallest amount of that food, and signal the immune system to release a chemical called histamine in the bloodstream along with other chemicals, which will cause a range of allergic signs and symptoms. Itchy eyes, dripping nose, rashes and hives, diarrhea, dry throat, labored breathing, nausea and even anaphylactic shock are the allergic responses that these chemicals are responsible for. Most food allergies are triggered by specific proteins that could be found in:


  • Fish
  • Eggs
  • Peanuts
  • Crabs, lobsters, shrimps or other shellfish
  • Walnuts, pecans or other tree nuts.


Food allergies in children are usually triggered by proteins that could be found in:


  • Tree nuts
  • Milk
  • Eggs
  • Peanuts


Chocolate rarely triggers a food allergy, despite the fact that it was long thought by some parents to cause food allergies in children.



Similar symptoms to a food allergy could be caused by a number of reactions to food. It is likely that a person doesn't have a true food allergy but food intolerance, in case they have digestive symptoms. They could be able to eat small amounts of problem foods without a reaction, depending on the type of food intolerance. However, even a tiny amount of food could trigger an allergic reaction in case they have a true food allergy. People frequently confuse food intolerance with food allergy because food intolerance has some of the same signs and symptoms of food allergy, including cramping, diarrhea, nausea and vomiting.


Because some people could be sensitive not to the food itself, but to a substance or ingredient that is used in the preparation of the food, diagnosing food intolerance could be quite tricky.


These are some of the common conditions that could cause symptoms, which are mistaken for a food allergy:


Irritable bowel syndrome:

The signs and symptoms of irritable bowel syndrome could be caused by certain foods. Someone may notice that certain foods will cause diarrhea, constipation or cramping. In order to avoid these symptoms, they should avoid those certain foods.


Absence of an enzyme needed to fully digest a food:

In some cases, people may not have adequate amounts of some enzymes that are needed to digest certain foods. For instance, someone's ability to digest lactose, which is the main sugar in milk products, will be reduced in case they have insufficient quantities of the enzyme lactase. Diarrhea, excess gas, bloating and cramping could be caused by lactose intolerance.


Sensitivity to food additives:

After eating certain food additives, some people could have digestive reactions in addition to other symptoms. For instance, an asthma attack could be triggered in sensitive people by sulfites, which is used to preserve dried fruit, wine and canned goods. Food colorings, artificial sweeteners and monosodium glutamate (MSG) are some of the other food additives that could trigger bad reactions.


Food poisoning:

Bacteria that are found in spoiled tuna and other fish could make a toxin that triggers harmful reactions. Some types of mushrooms and rhubarb are also toxic. Food poisoning could sometimes mimic an allergic reaction.


Psychological factors or recurring stress:

Although the reason of this is still not known, but sometimes the mere thought of a food could make a person sick.


Celiac disease:

Celiac disease is not a true food allergy, despite the fact that it's sometimes referred to as a gluten allergy. Although it involves an immune system response just like a food allergy, however, its unique immune system reaction is more complex than a simple food allergy. By eating gluten, the protein found in bread, cookies, pasta and many other foods containing wheat, rye or barley, celiac disease occurs in some people, which is a chronic digestive condition. When someone who has celiac disease eats foods containing gluten, an immune reaction will occur, which will cause damage to the surface of their small intestine and an inability to absorb certain nutrients. Sometimes, celiac disease could cause nutrient deficiencies and malnutrition. Abdominal pain, bloating and diarrhea are some of the signs and symptoms of celiac disease.



These are some of the complications that could occur due to food allergy:


  • Atopic dermatitis: Also called eczema, about one in three people with this condition also have a food allergy.
  • Migraines: In some people, histamines released by the immune system during an allergic reaction could trigger migraines.
  • Anaphylaxis: This is the most serious complication of a food allergy. It could be life-threatening.


It is thought that food allergies are linked to childhood hyperactivity and to arthritis, however, no evidence has been found to support this thesis.


Avoiding the foods that cause signs and symptoms is the only way of avoiding an allergic reaction. However, a person may come into contact with a food that causes a reaction in spite of their best efforts.


Over-the-counter or prescribed antihistamines could help reduce the symptoms of a minor allergic reaction. In order to help itching and hives, these drugs could be taken after exposure to an allergy-causing food. However, a severe allergic reaction cannot be treated with antihistamines.


A person might need an emergency injection of epinephrine and a trip to the emergency room in the case of a severe allergic reaction. Usually, people with allergies carry an autoinjector . This device is a combined syringe and concealed needle that injects a single dose of medication when pressed against the thigh. In case someone has been prescribed an epinephrine autoinjector, they should:


Always make sure to replace epinephrine before its expiration date, or it may not work properly.
Carry it with them at all times. Keeping an extra autoinjector in the car or in their desk at work could be a good idea.
Make sure that they know how to use it. They should also make sure that the people who are closest to them also know how to use the autoinjector because they could save the person's life if they're with the person in an anaphylactic emergency.


There still isn't any proven treatment that could prevent or completely relieve symptoms, however, there's ongoing research to find better treatments in order to reduce food allergy symptoms and prevent allergy attacks. Immunotherapy, also known as allergy shots, which consists of a series of injections that are used to reduce the effect of other allergies including hay fever, are not effective in treating food allergies.


Avoiding the food that is causing symptoms, and working with a doctor to identify what steps could be taken in order to relieve symptoms and how to spot and respond to a severe reaction is the best treatment available for now.


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