Skin Prick Test

The gold standard for allergy testing is as simple as pricking your skin, inserting a small amount of a substance, and waiting to see what happens. If you’re allergic to the substance, a reddish, elevated bump with a red ring around it will appear. This bump may be severely itchy.

An allergen is any substance that elicits an allergic reaction. When an allergen is inserted under a layer of your skin in a skin prick test, your immune system kicks into overdrive. It sends out antibodies to defend against what it believes to be a harmful substance.

When the allergen binds to a specific type of antibody, this triggers the release of chemicals, such as histamine. Histamine contributes to an allergic reaction. During this reaction, certain things happen in your body:

• Your blood vessels widen and become more porous.
• Fluid escapes from your blood vessels, which causes redness and swelling.
• Your body produces more mucus, which leads to congestion, runny nose, and teary eyes.
• Your nerve endings are stimulated, which causes itching, rash, or hives.
• Your stomach produces more acid.

Skin prick tests are usually performed on the inner forearm. Any number of allergens can be tested, as few as 3 or 4 or up to about 25 allergens. The following is a brief overview of how the test is performed.

• Clean arm with soap and water or alcohol.
• The forearm is coded with a skin marker pen corresponding to the number of allergens being tested. Marks should be at least 2 cm apart.
• A drop of allergen solution is placed beside each mark.
• A small prick through the drop is made to the skin using a sterile prick lancet. A new lancet must be used for each allergen tested.
• Excess allergen solution is dabbed off with a tissue.
• Observe skin reactions – if a reaction occurs it should do so within 20–30 minutes.