What is a skin test?
A skin test is a test done on the skin to identify if a substance (an allergen) is potentially triggering an allergic reaction. Environmental allergens (aeroallergens), including furry animals, dust mites, tree pollen, grass pollen, weed pollen, and molds can cause allergic eye symptoms, nasal symptoms, and asthma symptoms. Allergens that can trigger allergic reactions involving the skin, respiratory system, gastrointestinal system, and cardiovascular system include foods, medications, latex, and insect venoms.
How is an allergy skin test done?
Allergy skin testing is noninvasive and generally very well tolerated, even by small children. A small amount of the suspected allergy-provoking substance (the allergen) is placed on the skin. The skin is then gently punctured through the small drop with a special sterile puncture device. An allergy skin test is also called a prick/puncture test. The older terminology was "scratch test." With venoms, certain medications, such as penicillin, and in certain cases with aeroallergens, a second step of testing involves injecting a small amount of the allergen into the skin with a small needle. This is called an intradermal or an intracutaneous test. This type of testing should never be performed for foods.
What is a positive skin test result?
A positive skin test involves the formation of a bump (wheal) and redness (flare). In addition to the allergens in question, skin testing is also performed with a positive control (histamine) that should always cause a skin reaction, and a negative control, (saline), that should not cause a reaction. A test is positive if the allergen causes a wheal 3 mm greater than the negative control, and if the skin has a response to the histamine, as well. It is important to know that individuals cannot undergo skin testing if they are using antihistamines, since this blocks the histamine-mediated reaction.
For example, if a specific food allergy is suspected, a skin test uses a dilute extract of the suspected food. A small drop of this particular liquid extract is placed on the skin of the forearm or back. This underlying skin is gently punctured through the small drop with a special puncture device. The test is positive if there is a wheal and flare response described above. A positive test raises the possibility of a true allergy but is not diagnostic or confirmatory for having a true allergy. If there is no reaction with a wheal and flare, the test is read as negative and being allergic is very unlikely. If the skin test is positive, it implies that the patient has a type of antibody (IgE) on specialized cells in the skin that release histamine to cause symptoms of an allergic reaction. These cells are called mast cells and the IgE antibody bound to them is specific to the food being tested, like a puzzle piece. It is important to note that a positive skin test does not automatically mean a person is allergic to a food, medication, or aeroallergen. The skin test is one component of the information an allergist uses to make an accurate diagnosis, but the most important information comes from the patient's reported symptoms.
What are the advantages of skin tests?
Skin tests are rapid, simple, and relatively safe. They can be very helpful in specifically identifying causes of allergies.
Is there danger to a skin test?
In very rare cases, patients may have a severe allergic reaction involving multiple body systems to skin testing. For this reason, skin testing should be completed by an experienced allergist who is well prepared to diagnose and treat a severe allergic reaction. Although both are safe, intradermal or intracutaneous skin testing is more likely to cause a severe allergic reaction compared to prick/puncture testing.
What is done if a skin test can't be done?
For these patients, a doctor may use special blood tests, such as the RAST and the ELISA. These tests measure the presence of specific types of IgE in the blood.
These tests may cost more than skin tests, and results are not available immediately. As with skin testing, positive RAST and ELISA tests do not by themselves necessarily make the final diagnosis.
Health Solutions From Our Sponsors
Top Skin Test For Allergy Related Articles
Allergy (Allergies)An allergy refers to a misguided reaction by our immune system in response to bodily contact with certain foreign substances. When these allergens come in contact with the body, it causes the immune system to develop an allergic reaction in people who are allergic to it. It is estimated that 50 million North Americans are affected by allergic conditions. The parts of the body that are prone to react to allergies include the eyes, nose, lungs, skin, and stomach. Common allergic disorders include hay fever, asthma, allergic eyes, allergic eczema, hives, and allergic shock.
What Is Asthma? Symptoms, Causes, and TreatmentsWhat is asthma? What is the main cause of asthma? Learn information about asthma, a chronic disease of the bronchiole tubes. Discover information about asthma attacks, complications of asthma, and how to control an asthma attack.
Atopic DermatitisEczema is a general term for many types dermatitis (skin inflammation). Atopic dermatitis is the most common of the many types of eczema. Other types of eczema include: contact eczema, allergic contact eczema, seborrheic eczema, nummular eczema, stasis dermatitis, and dyshidrotic eczema.
Eczema and Atopic Dermatitis Rashes SlideshowEczema is a common allergic skin condition. Learn more about types of eczema like atopic dermatitis, dyshidrotic eczema and baby eczema. Find treatments like creams for face, hands, scalp, and more.
EczemaEczema refers to skin inflammation. There are many different types of eczema that produce symptoms and signs that range from oozing blisters to crusty plaques of skin. Treatment varies depending upon the type of eczema the person has.
Hives (Urticaria)Hives, also called urticaria, is a raised, itchy area of skin. Most often the cause of hives is unknown. Sometimes it is a sign of an allergic reaction to food or medications, but the cause of the allergy (the allergen) is unknown. Dermatographism and swelling (angioedema) may accompany hives. Treatment to get rid of hives and alleviate symptoms typically includes antihistamines.
How Long Does an Allergic Reaction Last?Allergic reactions may last for varying lengths of time. They may take a few hours to a few days to disappear. If the exposure to the allergen continues, such as during a spring pollen season, allergic reactions may last for longer periods such as a few weeks to months.
Nasal Allergy ReliefLearn how a combination of medication, preventing allergens, and allergy relief products can reduce allergy symptoms and help you feel better.
Poison Ivy, Oak, and SumacPoison ivy, oak, and sumac contain a substance called urushiol, which causes a rash on people who come in contact with them. Symptoms and signs include a red, swollen, itchy, blistering, bumpy rash. Treatment involves rinsing the exposed area with water, taking antihistamines and over-the-counter pain medications, using topical treatments such as calamine lotion, and applying cool compresses.
Skin RashThe word "rash" means an outbreak of red bumps on the body. The way people use this term, "a rash" can refer to many different skin conditions. The most common of these are scaly patches of skin and red, itchy bumps or patches all over the place.
Skin PictureThe skin is the largest organ of the body, with a total area of about 20 square feet. See a picture of the Skin and learn more about the health topic.
Skin QuizWhat's that all over you? Skin, of course! Test your knowledge of your most amazing organ with the Skin Quiz!
What Are the 4 Types of Allergic Reactions?Allergists recognize four types of allergic reactions: Type I or anaphylactic reactions, type II or cytotoxic reactions, type III or immunocomplex reactions and type IV or cell-mediated reactions.
What Does a Dermatologist Do?A dermatologist is a doctor who specializes in the diagnosis and treatment of health conditions of the hair, nails, and skin. They can diagnose and treat more than 3,000 diseases of the skin, hair, and nails, as well as cosmetic concerns.
What does microblading for eyebrows cost?Your eyebrows play a major role in defining and enhancing your facial features. Microblading is a kind of semi-permanent tattooing for your eyebrows. Microblading is an expensive procedure that costs between $500 and $2,000 per session.
10 Worst Cities for Spring AllergiesSee pictures of the top 10 "spring allergy capitals", according to the Asthma and Allergy Foundation of America (AAFA). From coast to coast, see if your city made the top 10.