What is Food Allergy?
Food allergy is an immune response to proteins found in food. Although people can have allergic reaction to any kind of food, there are foods that are more likely to trigger allergic response than others. The most common food allergies, according to the Food Allergy and Anaphylaxis Network, include dairy, soy, wheat, fish, shellfish, peanut, tree nut, and egg allergies. Food allergy is different from food intolerance (e.g. milk intolerance) and toxin-mediated reactions (e.g. bacterial toxins).
Some food allergies are outgrown by children when they reach a certain age. Soy, wheat, milk, and egg allergies are usually outgrown by children. Peanut allergy is usually not outgrown which is the reason why it is common among adults. Peanut and tree nut allergies are the major causes of allergy-related deaths in the U.S.
Allergic reaction occurs when the immune system mistakenly recognize food proteins as harmful. These proteins are tagged by antibodies called immunoglobulin E (IgE). IgE fools the immune system that the body is under attack by foreign invaders (food proteins) so it initiates an allergic response. In the process, histamine is released in the bloodstream causing the symptoms of food allergy.
What are the Symptoms of Food Allergy?
The symptoms of food allergy vary from person to person. The length of time the symptoms will appear from the time of exposure also vary. It can take as little as few minutes or may take several hours.
Food allergy symptoms in the skin include hives (red, itchy bumps), dermatitis, and swelling (edema). Besides the skin, swelling can also occur in the eyes and lips.
The gastrointestinal symptoms of food allergy include itchy bumps in mouth, metal taste in mouth, nausea, vomiting, diarrhea, and bloody stool in infants and children.
In the cardiorespiratory system, food allergy symptoms include runny nose, coughing, wheezing, breathing difficulty, blue coloring of lips & skin, weak pulse, pale skin, and fainting. Anaphylactic shock is the most dangerous symptoms of food allergies as well as other allergies. This fatal symptom is marked by a drop in blood pressure, breathing difficulty, serious itching & swelling, loss of consciousness, and coma.
What are the Treatments for Food Allergy?
People with food allergies need to consult their doctor for treatments and advices on how to manage their allergies.
Antihistamine medications are used to treat mild food allergy symptoms such as hives, swelling, etc. However, the dangerous anaphylactic shock should be treated with epinephrine injection.
Antihistamine blocks the action of histamine – substance that causes the noticeable allergy symptoms. Epinephrine reverses anaphylactic shock by improving blood circulation. It narrows the blood vessels to increase blood pressure and heart beat. Since epinephrine is injected directly to the blood, its effects are felt immediately.
Steroids are also used to treat food allergy by calming down the immune system cells. They can be taken orally, through injection, or through nasal spray. Steroids are not recommended in treating anaphylactic shock because it takes time before they take effect. Epinephrine is the appropriate treatment for anaphylactic shock.
People who are prone to anaphylactic shock are advised to bring with them injectable epinephrine (Epi-pen) in preparation for accidental consumption or exposure to food allergens. They are also advised to wear allergy warning bracelets.
What are the Tests for Food Allergy?
Ig-E mediated food allergy can be tested using skin prick test, blood test, and food challenge.
In skin prick test, small substance from food is placed in a small area of the skin pricked by a needle. The appearance of wheal or bump in the skin is considered positive.
In blood testing, IgE antibodies for a specific food allergen or protein are being detected and measured. RadioAllergoSorbent (RAST) test is an example of blood test for food allergy. The good thing about RAST test is its ability to screen hundreds of allergens from just a single sample.
Food challenge to test food allergy involves packaging the suspected food allergen into a capsule, giving it to the patient, and monitor the patient for symptoms of allergic reaction. Due to the risk of anaphylactic shock, the procedure is performed in the hospital environment and in the presence of physician.