Allergy testing is the process by which your doctor will identify the substance(s) to which you are allergic. If you have allergy symptoms (or have had an allergic reaction) and need to find out what caused it, an allergy test will be required.
Your health history and allergy test results are used to determine the cause of any severe reactions you may have experienced. Severe reactions that trigger an anaphylactic shock in your system will need an immediate diagnosis to identify the allergen(s).
If your risk of anaphylaxis is high, you should carry an epinephrine (adrenaline) auto-injector (EpiPen®) to treat the symptoms.
How Allergy Tests Work
Allergy tests measure your body’s response to specific allergy triggers or allergens. If you have an allergy, your immune system overreacts.
An allergy test measures your body’s response to different allergens to identify what substances trigger your symptoms.
There are three main types of allergens:
Inhaled allergens affect the body when your lungs or membranes of the nostrils or throat are exposed to them, for example, pollen.
Ingested allergens are present in certain foods, such as peanuts, soy, and seafood. An allergic reaction is triggered as the body digests the allergens.
Contact allergens trigger a reaction when they come in direct contact with your skin, for example, the rash or itch caused by poison ivy.
Depending on the suspected allergens and your symptoms, your allergist can use any of the following types of allergy tests for diagnosis.
Allergy Skin Tests
Skin tests for diagnosing allergies may use one of three methods:
Scratch Test – Also known as the prick test, this is usually the first test your doctor will use to identify allergens. During this procedure, your doctor will use a thin needle to prick the skin of your forearm or back with 10 to 50 types of allergens.
Alternatively, they will place droplets of potential allergens on your skin and use a device to scratch and lightly puncture the area so the liquid can enter your skin.
Adverse reactions, such as skin redness or rash, typically appear within 15 minutes if your system reacts to any of the allergens.
This test can check for airborne allergies, food allergies, and penicillin allergies.
Intradermal Test – This test may be needed if the scratch test gives inconclusive results. During this test, a small amount of the suspected allergen is injected into the outer layer of your skin, and the body’s reaction is noted.
This test can check for allergies to airborne irritants, medications, and insect stings.
Patch Test – During this test, the doctor will apply a patch (bandage) with the allergen to your skin. The patch is left on your body for 48 to 96 hours. You may need to return to your doctor’s office during this time for review.
The allergen is identified if any reactions are seen on the skin.
This test can be used to determine the allergens that cause contact dermatitis.
Antibiotic (Penicillin) Sensitivity Test
Penicillin allergy is one of the most common drug allergies seen in people. Penicillin is an antibiotic medicine used in the treatment of a variety of many serious ailments.
Sensitivity to penicillin can cause symptoms such as hives, rash, and itching. Some people might also have a severe reaction to penicillin that can trigger anaphylaxis, a life-threatening condition that affects multiple biological systems in the body.
Before a penicillin sensitivity test is administered, it is recommended that you avoid using antihistamines to ensure that the results are accurate.
A saline solution and a histamine solution are first applied to the skin to ensure that your skin reacts normally.
If the saline solution causes a reaction, your skin is too sensitive, and the test will not be accurate. The histamine solution may cause a red, raised, itchy area, like a mosquito bite. If there is no reaction, the test may not show accurate results.
Sensitivity to penicillin is checked using the scratch test and the intradermal test.
Allergy Blood Testing (For Difficult to Diagnose Allergies)
Allergy blood testing is a method to test your blood to check for signs of allergies. The test looks for Immunoglobulin E (IgE) in blood.
This test successfully detects IgE antibodies to major allergens in the blood. If your blood contains IgE antibodies specific to a particular substance, you are allergic to that substance.
This type of testing is sometimes performed as an alternative to the allergy skin test. However, results for the blood test can take up to 2 days, while the skin test shows results within 15 minutes.
The ingestion challenge is an oral food challenge (OFC). It is a medical procedure in which a suspected food allergen is eaten slowly, in gradually increasing amounts, under medical supervision to diagnose or rule out a true food allergy accurately.
This test should always be performed by a doctor who specializes in allergies. If you develop anaphylaxis during the test, the doctor can quickly resolve the problem with an epinephrine injection to stop the reaction.
Preparing for Your Allergy Test
Allergy testing allows you to discover what is causing your allergic reactions. It is a great way to figure out your triggers and create an action plan to avoid and minimize your triggers and stay healthy.
If you have an allergy test scheduled, there are a few things you can do to prepare for your allergy test and ensure you get the most accurate results.
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