Contents:
- Medical Video: Skin Prick Test (Allergy Test) - John Hunter Children's Hospital
- Types of allergens
- Why allergy testing is done
- How to prepare for allergy testing
- How allergy testing is done
- Risk of allergic tests
- After allergy testing
Medical Video: Skin Prick Test (Allergy Test) - John Hunter Children's Hospital
An allergy test is a test carried out by an allergist to determine whether your body has an allergic reaction to a known substance. Tests can be blood tests, skin tests, or food elimination.
Allergies occur when your immune system overreacts to something in your environment. For example, pollen, which is usually harmless, can cause your body to overreact. The body's excessive reaction to substances that can cause symptoms such as runny nose, sneezing, sinus blockage, and watery eyes.
Types of allergens
There are three types of allergens (substances that can cause allergic reactions):
- Inhaled allergens: These allergens affect the body when they come into contact with the lungs or nasal membranes. Pollen is the most common inhalation allergen.
- Swallowed allergens: These allergens are present in certain foods such as peanuts, soybeans, and gluten.
- Skin allergens: these allergens come in contact with your skin to produce a reaction, such as a rash and itching caused by poison ivy.
An allergy test involves giving a person exposure to a very small amount of certain allergens and seeing the reaction that occurs.
Why allergy testing is done
The World Allergy Organization estimates that allergies are responsible for 250,000 deaths annually (WAO).
An allergy test is done to determine whether certain pollen, fungi, or other allergens cause someone to be allergic. You might need medication to treat your allergies or you might just try to avoid triggering your allergies.
How to prepare for allergy testing
Before testing your allergy, the doctor will ask about your lifestyle, family history, and more.
You will most likely be told to stop taking the following medication before your allergy test, because the drug can affect the test results:
- Antihistamines (both prescription drugs and drugs on the market)
- Certain heartburn medications
- Omalizumab (Xolair) (asthma medication)
- Tricyclic antidepressants
How allergy testing is done
An allergy test might be done with a skin test or a blood test. In cases of suspected food allergies, you can do a diet elimination.
Skin test
Skin tests are used to identify various potential allergens. This includes air allergens, food, and contact allergens.
Your doctor will usually try the initial test first. During this test, allergens are placed on the part of your skin. A technician uses a special tool to scratch the surface of the skin. You will be closely monitored to see how your skin reacts to foreign substances. If there is no swelling or redness on the skin, you are not allergic to these allergens.
If the initial test is not convincing, your doctor may order an intradermal skin test. This test is done by injecting a small amount of allergens into your skin. Again, the doctor will monitor your reaction.
Another form of allergic skin test is a patch test. This test is done using an adhesive patch that is attached to a suspected allergen. The patch will remain on your body after you leave your doctor's office. The patch is then checked 24 hours after application and again at 48 hours, if needed.
Blood test
In the case of a severe allergic reaction, the doctor can determine that the skin test will not be effective. Therefore, he can choose to take your blood sample. Blood is then tested in a laboratory to examine the presence of antibodies that fight certain allergens. This test, called ImmunoCAP, is very successful in detecting antibodies to the main allergens.
Food elimination
Food elimination can help doctors determine which foods cause you to have an allergic reaction. This method requires someone to avoid food from their diet and then consume them again. Your reaction will help determine the foods that cause allergies.
Risk of allergic tests
Allergy tests can cause mild itching, redness, or swelling of the skin. Sometimes, small lumps called patches appear on the skin. These symptoms often occur within a few hours, but can last for several days. A mild cortisone cream can relieve these symptoms.
In rare cases, allergy testing causes a direct allergic reaction that requires medical attention. In anticipation of such a reaction, an allergy test must be carried out in a clinic equipped with adequate medicines and equipment. This includes epinephrine to treat anaphylaxis (a life-threatening allergic reaction).
If you experience a severe reaction after you leave the doctor's office, contact your doctor immediately. If you experience anaphylactic symptoms - such as throat swelling, difficulty breathing, or low blood pressure, immediately rush to the hospital because this is a medical emergency.
After allergy testing
After the doctor determines the allergens that cause your symptoms, he will instruct you on how to avoid allergens. Your doctor can also suggest drugs that can relieve your symptoms.
