An allergy is an overreaction, also known as a hypersensitivity, of the body's immune system. Normally, your immune system works to fight off foreign substances like viruses and bacteria. When you have an allergy, your immune system treats a harmless substance, like dust or pollen, as a threat. To fight this perceived threat, your immune system reacts and causes an allergic reaction. Symptoms of an allergic reaction can range from sneezing and a stuffy nose to a life-threatening condition known as anaphylactic shock.
There are four main types of overreactions, known as Type 1 through Type IV hypersensitivities. Type 1 hypersensitivity causes some of the most common allergies. These include dust mites, pollens, foods, and animal dander. Other types of hypersensitivities cause different immune system overreactions. These range from mild skin rashes to serious autoimmune disorders.
An allergy skin test usually checks for allergies caused by Type 1 hypersensitivity. The test looks for reactions to specific allergens that are placed on the skin.
Other names: type 1 hypersensitivity skin test, hypersensitivity test allergy scratch test, allergy patch test, intradermal test
An allergy skin test is used to diagnose certain allergies. The test can show which substances (allergens) are causing your allergic reaction. These substances may include pollen, dust, molds, and medicines such as penicillin. The tests are not usually used to diagnose food allergies. This is because food allergies are more likely to cause anaphylactic shock.
Your health care provider may order allergy testing if you have symptoms of an allergy. These include:
There is very little risk to having allergy skin tests. The test itself is not painful. The most common side effect is red, itchy skin at the test sites. In very rare cases, an allergy skin test may cause anaphylactic shock. This is why skin tests need to be done in a provider's office where emergency equipment is available. If you've had a patch test and feel intense itching or pain under the patches once you are home, remove the patches and call your provider.
