A food allergy is when the body’s immune system reacts unusually to specific foods. Although allergic reactions are often mild, they can be very serious. 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.

What causes food allergies?

Food allergies happen when the immune system – the body’s defense against infection – mistakenly treats proteins found in food as a threat. As a result, a number of chemicals are released. It’s these chemicals that cause the symptoms of an allergic reaction.

While any food can cause an adverse reaction, eight types of food account for about 90 percent of all reactions:

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

Types of food allergies

Food allergies are divided into 3 types, depending on symptoms and when they occur.

  • IgE-mediated food allergy – the most common type, triggered by the immune system producing an antibody called immunoglobulin E (IgE). Symptoms occur a few seconds or minutes after eating. There’s a greater risk of anaphylaxis with this type of allergy.
  • non-IgE-mediated food allergy – these allergic reactions aren’t caused by immunoglobulin E, but by other cells in the immune system. This type of allergy is often difficult to diagnose as symptoms take much longer to develop (up to several hours).
  • mixed IgE and non-IgE-mediated food allergies – some people may experience symptoms from both types.

Symptoms

Symptoms of an allergic reaction may involve the skin, the gastrointestinal tract, the cardiovascular system and the respiratory tract. They can surface in one or more of the following ways:

  • Vomiting and/or stomach cramps
  • Hives
  • Shortness of breath
  • Wheezing
  • Repetitive cough
  • Shock or circulatory collapse
  • Tight, hoarse throat; trouble swallowing
  • Swelling of the tongue, affecting the ability to talk or breathe
  • Weak pulse
  • Pale or blue coloring of skin
  • Dizziness or feeling faint
  • Anaphylaxis, a potentially life-threatening reaction that can impair breathing and send the body into shock; reactions may simultaneously affect different parts of the body (for example, a stomachache accompanied by a rash)

Most food-related symptoms occur within two hours of ingestion; often they start within minutes. In some very rare cases, the reaction may be delayed by four to six hours or even longer. Delayed reactions are most typically seen in children who develop eczema as a symptom of food allergy and in people with a rare allergy to red meat caused by the bite of a lone star tick.

Diagnosing Food Allergies

A food allergy will usually cause some sort of reaction every time the trigger food is eaten. Symptoms can vary from person to person, and you may not always experience the same symptoms during every reaction. Allergic reactions to food can affect the skin, respiratory tract, gastrointestinal tract and cardiovascular system. It is impossible to predict how severe the next reaction might be, and all patients with food allergies should be carefully counseled about the risk of anaphylaxis, a potentially fatal reaction that is treated with epinephrine (adrenaline).

To make a diagnosis, allergists ask detailed questions about your medical history and your symptoms. Be prepared to answer questions about:

  • What and how much you ate
  • How long it took for symptoms to develop
  • What symptoms you experienced and how long they lasted.

After taking your history, your allergist may order skin tests and/or blood tests, which indicate whether food-specific immunoglobulin E (IgE) antibodies are present in your body:

  • Skin-prick tests provide results in about 20 – 30 minutes. A liquid containing a tiny amount of the food allergen is placed on the skin of your arm or back. Your skin is pricked with a small, sterile probe, allowing the liquid to seep under the skin. The test, which isn’t painful but can be uncomfortable, is considered positive if a wheal (resembling the bump from a mosquito bite) develops at the site where the suspected allergen was placed. As a control, you’ll also get a skin prick with a liquid that doesn’t contain the allergen; this should not provoke a reaction, allowing comparison between the two test sites.
  • Blood tests, which are a bit less exact than skin tests, measure the amount of IgE antibody to the specific food(s) being tested. Results are typically available in about a week and are reported as a numerical value.

Your allergist will use the results of these tests in making a diagnosis. A positive result does not necessarily indicate that there is an allergy, though a negative result is useful in ruling one out.

Management and Treatment

The primary way to manage a food allergy is to avoid consuming the food that causes you problems. Carefully check ingredient labels of food products, and learn whether what you need to avoid is known by other names.

Avoid making any radical changes, such as cutting out dairy products, to your or your child’s diet without first talking to your Doctor For some foods, such as milk, you may need to speak to a dietitian before making any changes.

Antihistamines can help relieve the symptoms of a mild or moderate allergic reaction. A higher dose of antihistamine is often needed to control acute allergic symptoms. Adrenaline is an effective treatment for more severe allergic symptoms, such as anaphylaxis.

People with a food allergy are often given a device known as an auto-injector pen, which contains doses of adrenaline that can be used in emergencies.

Do you suspect you’re suffering from a food allergy? Dr. Shahid Abbas, Consultant – Allergy and Immunology can evaluate your symptoms and determine the source and treatment.

Reference

Disclaimer: All contents on this site are for general information and in no circumstances information be substituted for professional advice from the relevant healthcare professional, Writer does not take responsibility of any damage done by the misuse or use of the information.