What Is an Allergy Scratch Test?

Many times people experience allergic reactions, yet are unsure exactly what they are allergic to. An allergy scratch test exposes a person to small amounts of common allergens to determine what allergens are causing a reaction.

When Do I Need an Allergy Test?

• A physician may recommend an allergy scratch test if a person is experiencing allergy symptoms such as itchy eyes, chest congestion, hives, eczema or abdominal cramping after eating. The test can pinpoint the exact cause of symptoms, which gives physicians a cue for treatment.

What Allergies Will I Be Tested For?

• A scratch test can test for as many as 36 allergens at a time. The type of reaction a person is experiencing may determine how many allergens will be tested for. Allergens include dust mites, pets, molds, trees, grasses, pollens, insect venoms, foods, latex or medications.

How Does the Test Work?

• A scratch test is performed on the forearm (adults) or the back (children). Individual drops of the allergen are dropped on the area that is coded with a marker, and a physician makes light pricks with a needle to allow the fluid to absorb. It is important to note that the pricks do not cause bleeding or scarring. The fluid absorbs for 20 minutes or less, and a doctor assesses the reaction on the skin.

How Are Results Determined?

• After enough time has passed, if the skin on a particular allergen has turned into a hive or is swollen and red, the person is allergic to some degree to that allergen. If the hive is particularly large, the allergy is more severe. The reaction may appear similar to a mosquito bite and typically subsides within 30 minutes.

Side Effects

• Although the skin is exposed to allergens, only a small percentage of patients experience a severe reaction. While some discomfort or itching may occur, the test generally does not cause any further reactions.