Food Allergy

As the name implies, this is a reaction or an allergic reaction to certain food or foods. Food allergy is an immune system reaction that occurs soon after eating a certain food. People with a food allergy have an immune system that reacts to certain proteins found in food. Their immune system attacks these compounds as if it were a harmful pathogen, such as a bacterium or virus in the sense that even a tiny amount of the allergy-causing food can trigger signs and symptoms such as digestive problems, hives or swollen airways. In some people, a food allergy can cause severe symptoms or even a life-threatening reaction known as anaphylaxis.

According to Center for Disease Control and Prevention (CDC), food allergies are estimated to affect 4 to 6 percent of children and 4 percent of adults. Food allergy symptoms are most common in babies and children, but they can appear at any age. You can even develop an allergy to foods you have eaten for years with no problems.

It’s easy to confuse a food allergy with a much more common reaction known as food intolerance. However, food intolerance is a less serious condition that does not involve the immune system.



In food allergies, the immune system treats a specific protein in a food as a harmful substance, a pathogen, something that may cause disease. It responds by producing antibodies to attack this protein. This antibody is immunoglobulin E (IgE) released to neutralize the allergy-causing food or food substance (the allergen).

When that same food is eaten next, the antibodies senses it and then signals the immune system to react immediately. The immune system reacts by releasing histamine and other substances or chemicals into the bloodstream. Histamine and these other chemicals cause the symptoms of food allergies.

Histamine causes blood vessels to dilate (expand) and the skin to become inflamed (swollen). It also affects the nerves, making the person feel itchy. The nose may produce more mucous, resulting in itching, burning, and a streaming nose.

In adults, the majority of food allergies are triggered by certain proteins in:

  • Shellfish, such as shrimp, lobster and crab
  • Peanuts
  • Tree nuts, such as walnuts and pecans
  • Fish

In children, food allergies are commonly triggered by proteins in:

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


Pollen-food allergy syndrome

Also known as oral allergy syndrome, pollen-food allergy syndrome affects many people who have hay fever. In this condition, certain fresh fruits and vegetables or nuts and spices can trigger an allergic reaction that causes the mouth to tingle or itch. In serious cases, the reaction results in swelling of the throat or even anaphylaxis.

Proteins in certain fruits, vegetables, nuts and spices cause the reaction because they’re similar to allergy-causing proteins found in certain pollens. This is an example of cross-reactivity. However, when you cook foods that trigger pollen-food allergy syndrome, your symptoms may be less severe.


Exercise-induced food allergy

Eating certain foods may cause some people to feel itchy and lightheaded soon after starting to exercise. Serious cases may even involve hives or anaphylaxis. Not eating for a couple of hours before exercising and avoiding certain foods may help prevent this problem.


Food intolerance and other reactions

A food intolerance or a reaction to another substance eaten may cause the same signs and symptoms as a food allergy does such as nausea, vomiting, cramping and diarrhea. Depending on the type of food intolerance eaten, one may be able to eat small amounts of problem foods without a reaction. However, this is not the case with someone with a true food allergy because even a tiny amount of food may trigger an allergic reaction.

One of the tricky aspects of diagnosing food intolerance is that some people are sensitive not to the food itself but to a substance or ingredient used in the preparation of the food.


Common conditions that can cause symptoms mistaken for a food allergy include:

Absence of an enzyme needed to fully digest a food

That is having inadequate amounts of some enzymes needed to digest certain foods. Insufficient quantities of the enzyme lactase, for example, reduces the ability to digest lactose, the main sugar in milk products and this (lactose intolerance) can cause bloating, cramping, diarrhea and excess gas.

Food poisoning

Other times, food poisoning can mimic an allergic reaction. For instance, bacteria in spoiled tuna and other fish also can make a toxin that triggers harmful reactions.

Sensitivity to food additives

Some people have digestive reactions and other symptoms after eating certain food additives. For example, sulfites used to preserve dried fruit, canned goods and wine can trigger asthma attacks in sensitive people.

Histamine toxicity

Certain fish, such as tuna or mackerel, that are not refrigerated properly and that contain high amounts of bacteria may also contain high levels of histamine that trigger symptoms similar to those of food allergy. Rather than an allergic reaction, this is known as histamine toxicity or scombroid poisoning.

Celiac disease

While celiac disease is sometimes referred to as a gluten allergy, it does not result in anaphylaxis. Like a food allergy, it does involve an immune system response, but it’s a unique reaction that’s more complex than a simple food allergy. This chronic digestive condition is triggered by eating gluten, a protein found in bread, pasta, cookies, and many other foods containing wheat, barley or rye. Hence it is not advisable for someone with celiac disease to eat food that contains gluten because when this happens, an immune reaction occurs that causes damage to the surface of your small intestine, leading to an inability to absorb certain nutrients.



Food allergy risk factors include:

  • Family history. One is at an increased risk of food allergies if asthma, eczema, hives or allergies such as hay fever are common in the family.


  • Other allergies. Being allergic to one food is also a factor for one becoming allergic to another. Similarly, having other types of allergic reactions, such as hay fever or eczema, puts one at risk of having a food allergy.


  • Age. Food allergies are more common in children, especially toddlers and infants. However, they grow older, their digestive system matures making the body less likely to absorb food or food components that trigger allergies. Fortunately, children typically outgrow allergies to milk, soy, wheat and eggs, whereas, severe allergies and allergies to nuts and shellfish are more likely to be lifelong.


  • Asthma. Asthma and food allergy commonly occur together. When they do, both food allergy and asthma symptoms are more likely to be severe.


Factors that may increase the risk of developing an anaphylactic reaction include:

  • Having a history of asthma
  • Being a teenager or younger
  • Delaying use of epinephrine to treat your food allergy symptoms
  • Not having hives or other skin symptoms



Complications of food allergy can include:

  • Anaphylaxis. This is a life-threatening allergic reaction.
  • Atopic dermatitis (eczema). Food allergy may cause a skin reaction, such as eczema.



An allergic reaction to a particular food may be uncomfortable but not severe for a number of person, however this is not the case with some that can be frightening and even life-threatening. Food allergy symptoms usually develop within a few minutes to two hours after eating the offending food.

The most common food allergy signs and symptoms include:

  • Tingling or itching in the mouth
  • Hives, itching or eczema
  • Swelling of the lips, face, tongue and throat or other parts of the body
  • Wheezing, nasal congestion or trouble breathing
  • Abdominal pain, diarrhea, nausea or vomiting
  • Dizziness, lightheadedness or fainting



Food allergy can trigger a severe allergic reaction called anaphylaxis, however, this is observe in everyone allergic to food. It usually occurs soon after exposure to the specific allergen, but can take a few hours. This can cause life-threatening signs and symptoms, including:

  • Constriction and tightening of the airwaysShock with a severe drop in blood pressureDizziness, lightheadedness or loss of consciousnessitchy, tickly throat
  • fear, a feeling of apprehension
  • Rapid pulse or accelerated heartbeat
  • A swollen throat or the sensation of a lump in your throat that makes it difficult to breathe
  • nausea
  • skin is itchy, rash may spread rapidly and cover much of the body
  • sneezing
  • streaming nose and eyes
  • throat, lips, face, and mouth swell rapidly
  • vomiting
  • loss of consciousness

Emergency treatment is critical for anaphylaxis. Untreated, anaphylaxis can cause a coma or even death.



There’s no perfect test used to confirm or rule out a food allergy. Doctors however, do consider a number of factors before making a diagnosis. These factors include.

The symptom(s). it is mandatory that you give your doctor a detailed history of the observed symptoms, the foods, and how much, seem to cause problems.

Family history of allergies. Also share information about members of your family who have allergies of any kind.

A physical examination. A careful exam can often identify or exclude other medical problems.

A skin test. A skin prick test can determine one’s reaction to a particular food. In this test, a small amount of the suspected food is placed on the skin of the forearm or back. A doctor or another health professional then pricks the skin with a needle to allow a tiny amount of the substance beneath your skin surface. If one allergic to that particular substance being tested, there will be a development of or a raised bump or reaction. Keep in mind, a positive reaction to this test alone isn’t enough to confirm a food allergy.

A blood test. A blood test is used to measure the immune system’s response to particular foods by measuring the allergy-related antibody known as immunoglobulin E (IgE).

For this test, a blood sample taken to a medical laboratory, where different foods can be tested.

Elimination diet. This is rather easy, one may be asked to eliminate suspect foods for a week or two and then add the food items back into taken diet one at a time. This process can help link symptoms to specific foods. However, elimination diets aren’t foolproof.

An elimination diet can’t tell you whether one’s reaction to a food is a true allergy instead of a food sensitivity. This may not be safe for someone who has had a severe reaction to a food in the past.

Oral food challenge. During this test, one is been given small but increasing amounts of the food suspected of causing the symptoms. If there is no reaction during this test, then, it is consider safe to include the tested food in one’s diet again.



Elimination diet: As earlier said, elimination is the best way to avoid food allergy that’s is avoiding the food(s) that causes the allergic reactions. However, it is important that the food removed does not in any way undermine the individual’s health, hence seeing and using a dietician is important. For instance, if the allergy is just to peanuts, there will be no health consequences if the individual never eats peanuts again. However, an allergy to milk means finding other sources of calcium and protein.

Elimination may not simply mean not eating the particular food; it may also include never inhaling it, touching it, or eating foods with traces of it inside. Cutlery, crockery, cooking surfaces, and chopping boards must be free of the allergen.

Patients will need to read food and drink labels carefully. Even some soaps, pet foods, glues, and adhesives may have traces of a food allergen.

When eating out, being vigilant can be particularly difficult but a necessary factor.


Medication for emergencies

Antihistamines – these will come in the form of gels, liquids, or tablets. They are usually effective for patients with mild or moderate allergies. Histamines are chemicals which cause most allergy symptoms, and antihistamines block their effects.

Epinephrine (adrenaline) – this is used by individuals who have food allergies that may result in anaphylaxis. Epinephrine keeps blood pressure up by constricting blood vessels, as well as easing the airways. People who have had severe allergic reactions should carry an epinephrine auto-injector with them, for instance, the EpiPen, EpiPen Jr., Twinject, or Anapen.



  • Dermatology Research and Practice, National Institute for Health and Clinical Excellence (NICE), American College of Allergy, Asthma and Immunology, British Society for Allergy & Clinical Immunology (BSACI), Allergy U.K.




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