Skin Tests for Allergies
Skin tests for allergies are performed to find out the substances which are causing allergic symptoms. These tests are done by applying an extract of certain allergen to the skin, pricking or scratching the skin to get it exposed to the allergen and then observing the skin’s reaction. Another way of applying the extract is to directly inject the allergen into the skin patch and leaving it for some time period.
The three major skin tests for allergies are discussed below. They include scratch test, patch test and intradermal test.
Types of skin tests for allergies
- Scratch test (Prick or puncture test)
Prior to the test, the skin on the forearm is examined and it is cleaned using alcohol. Certain areas are marked on the skin to apply each allergen for testing. A drop of extract is applied in each of the corresponding marks, one with each animal dander, insect venom or pollen. A pricking device is used to prick the skin so that the extract enters into the epidermal skin layer. This pricking causes no bleeding. This scratch test takes about 5 – 10 minutes to place the allergen and to examine the skin reaction, it takes 15 minutes.
- Patch test
This type of skin test is done by placing a patch on the skin which is completely filled with allergen extract. This is performed mostly to find out the trigger of allergic contact dermatitis. The skin develops itching sensation and gets irritated when there are allergy causing antibodies in the body system. This clearly shows that the body is allergic to that particular substance. This test takes longer time since you need to wear the patch for about 48 hours.
- Intradermal test
In this type of skin test for allergies, a small amount of extract is injected into the skin to examine the allergic reaction. This test also takes the same time as scratch test takes.
These are the most important major types of skin tests for allergies. They help in easy determination of types of allergies.
Are these allergy tests safe, how much time they take, how one can prepare and what happens during these tests may be the question running around your mind. The following solves all these doubts if you have any.
Are skin tests for allergies safe?
These tests are safe when performed in a proper manner. Since only a few amounts of allergen are introduced, it is considered to be safe. For some people, the tests may be mildly irritating.
How to prepare for the test?
Inform the physician who is performing the skin test about all the medications you are taking. As the antihistamines help to stop allergic reactions, you should stop taking them for some days before the test. Your physician even gives you a list of medications that you should avoid taking before the skin tests. Certain medications cannot be discontinued. In this case, the physician performs a control test to check whether the particular drug interferes with any of the skin tests.
How much time does skin test for allergy takes?
You need to spend about one hour for the complete procedure. For scratch and intradermal tests, it takes 5 – 10 minutes to place the allergen. It takes more 15 minutes for the reaction to occur.
Patch tests take longer time as the patch should be worn for nearly 48 hours. When the patch is worn, you should avoid bathing and have to return to the physician after a certain time period.
What happens after skin tests?
If there are any extracts or ink marks after the tests, they can be wiped off using alcohol. If there is any itching sensation, you can apply a mild cortisone cream to the site.
In case of a patch test, the bandages can be removed only after 48 hours. You need to be careful by avoiding these areas getting wet and should return to the physician for removal of the bandage.
If you experience any symptoms like wheezing, lightheadedness, fever, extensive rash, shortness of breath, difficulty in swallowing and swelling of lips, face or mouth, you can consult a physician immediately.
This is all about skin tests for allergies and questions that one can come across when undergoing these tests.