What to do before food allergy test
If your GP suspects a food allergy, you may be referred to an allergy clinic for testing.
The tests needed can vary, depending on the type of allergy:
- if the symptoms developed quickly (an IgE-mediated food allergy) – you’ll probably be given a skin-prick test or a blood test
- if the symptoms developed more slowly (non-IgE-mediated food allergy) – you’ll probably be put on a food elimination diet
During a skin-prick test, drops of standardised extracts of foods are placed on the arm.
The skin is then pierced with a small lancet, which allows the allergen to come into contact with the cells of your immune system.
Occasionally, your doctor may perform the test using a sample of the food thought to cause a reaction.
Itching, redness and swelling generally indicates a positive reaction. This test is generally painless.
A skin-prick test does own a little theoretical chance of causing anaphylaxis, but testing will be carried out where there are facilities to deal with this – usually an allergy clinic, hospital, or larger GP surgery.
An alternative to a skin-prick test is a blood test, which measures the quantity of allergic antibodies in the blood.
Food elimination diet
In a food elimination diet, the food thought to own caused the allergic reaction is withdrawn from your diet for 2 to 6 weeks.
The food is then reintroduced.
If the symptoms go away when the food is withdrawn but return once the food is introduced again, this normally suggests a food allergy or intolerance.
Before starting the diet, you should be given advice from a dietitian on issues such as:
- the food and drinks you need to avoid
- how you should interpret food labels
- if any alternative sources of nutrition are needed
- how endless the diet should final
Don’t attempt a food elimination diet by yourself without discussing it with a qualified health professional.
Will I need to do anything to prepare for the test?
You don’t need any special preparations for a food allergy test.
There are several shop-bought tests available that claim to detect allergies, but should be avoided.
- vega testing – claims to detect allergies by measuring changes in your electromagnetic field
- kinesiology testing – claims to detect food allergies by studying your muscle responses
- hair analysis – claims to detect food allergies by taking a sample of your hair and running a series of tests on it
- alternative blood tests (leukocytotoxic tests) – claim to detect food allergies by checking for the «swelling of white blood cells»
Many alternative testing kits are expensive, the scientific principles they are allegedly based on are unproven, and independent reviews own found them to be unreliable.
They should therefore be avoided.
What is food allergy testing?
A food allergy is a condition that causes your immune system to treat a normally harmless type of food as if was a dangerous virus, bacteria, or other infectious agent. The immune system response to a food allergy ranges from mild rashes to abdominal pain to a life-threatening complication called anaphylactic shock.
Food allergies are more common in children than adults, affecting about 5 percent of children in the United States.
Numerous children outgrow their allergies as they get older. Almost 90 percent of every food allergies are caused by the following foods:
- Tree nuts (including almonds, walnuts, pecans, and cashews)
For some people, even the tiniest quantity of the allergy-causing food can trigger life-threatening symptoms. Of the foods listed above, peanuts, tree nuts, shellfish, and fish generally cause the most serious allergic reactions.
Food allergy testing can discover out whether you or your kid has a food allergy.
If a food allergy is suspected, your primary care provider or your child’s provider will probably refer you to an allergist. An allergist is a doctor who specializes in diagnosing and treating allergies and asthma.
Other names: IgE test, oral challenge test
What is it used for?
Food allergy testing is used to discover out if you or your kid has an allergy to a specific food. It may also be used to discover out whether you own a true allergy or, instead, a sensitivity to a food.
Food sensitivity, also called food intolerance, is often confused with a food allergy. The two conditions can own similar symptoms, but complications can be extremely different.
A food allergy is an immune system reaction that can affect organs throughout the body.
It can cause dangerous health conditions. Food sensitivity is generally much less serious. If you own a food sensitivity, your body can’t properly digest a certain food, or a food bothers your digestive system. Symptoms of food sensitivity are mostly limited to digestive problems such as abdominal pain, nausea, gas, and diarrhea.
Common food sensitivities include:
- Lactose, a type of sugar found in dairy products. It may be confused with a milk allergy.
- MSG, an additive found in numerous foods
- Gluten, a protein found in wheat, barley, and other grains. It is sometimes confused with a wheat allergy.
Gluten sensitivity and wheat allergies are also diverse from celiac disease. In celiac disease, your immune system damages your little intestine when you eat gluten. Some of the digestive symptoms can be similar, but celiac disease is not a food sensitivity or a food allergy.
Why do I need food allergy testing?
You or your kid may need food allergy testing if you own certain risk factors and/or symptoms.
Risk factors for food allergies include having:
- A family history of food allergies
- Other food allergies
- Other types of allergies, such as hay fever or eczema
Symptoms of food allergies generally affect one or more of the following parts of the body:
- Skin. Skin symptoms include hives, tingling, itching, and redness.
In babies with food allergies, the first symptom is often a rash.
- Digestive system. Symptoms include abdominal pain, metallic taste in the mouth, and swelling and/or itching of the tongue.
- Respiratory system (includes your lungs, nose, and throat). Symptoms include coughing, wheezing, nasal congestion, trouble breathing, and tightness in the chest.
Anaphylactic shock is a severe allergic reaction that affects the entire body. Symptoms may include those listed above, as well as:
- Rapid swelling of the tongue, lips, and/or throat
- Fast pulse
- Pale skin
- Tightening of the airways and trouble breathing
- Feeling faint
Symptoms can happen just seconds after someone is exposed to the allergic substance.
Without quick medical treatment, anaphylactic shock can be fatal. If anaphylactic shock is suspected, you should call 911 immediately.
If you or your kid is at risk for anaphylactic shock, your allergist may prescribe a little device you can use in an emergency. The device, which is called an auto-injector, delivers a dose of epinephrine, a medicine that slows below the allergic reaction.
You will still need to get medical assist after using the device.
What happens during food allergy testing?
The testing may start with your allergist performing a physical exam and asking about your symptoms. After that, he or she will act out one or more of the following tests:
- Oral challenge test. During this test, your allergist will give you or your kid little amounts of the food suspected of causing the allergy.
The food may be given in a capsule or with an injection. You’ll be closely watched to see if there is an allergic reaction. Your allergist will provide immediate treatment if there is a reaction.
- Elimination diet. This is used to discover which specific food or foods is causing the allergy. You’ll start by eliminating every suspected foods from your child’s or your diet. You will then add the foods back to the diet one at a time, looking for an allergic reaction.
An elimination diet can’t show whether your reaction is due to a food allergy or a food sensitivity. An elimination diet is not recommended for anyone at risk for a severe allergic reaction.
- Skin prick test. During this test, your allergist or other provider will put a little quantity of the suspected food on the skin of your forearm or back. He or she will then prick the skin with a needle to permit a tiny quantity of the food to get beneath the skin. If you get a red, itchy bump at the injection site, it generally means you are allergic to the food.
- Blood test. This test checks for substances called IgE antibodies in the blood.
IgE antibodies are made in the immune system when you are exposed to an allergy-causing substance. During a blood test, a health care professional will take a blood sample from a vein in your arm, using a little needle. After the needle is inserted, a little quantity of blood will be collected into a test tube or vial.
You may feel a little sting when the needle goes in or out. This generally takes less than five minutes.