Skin tests may be done to diagnose rashes, moles, skin allergies, food allergies, bacterial or fungal skin infections, and other diseases. Skin tests are also done to tell the difference between cancer (malignant) cells and noncancer (benign) growths.
Skin tests for allergies include:
Patch testing. Patch tests are used to help diagnose skin allergies leading to contact dermatitis. Small amounts of substances that may cause an allergic reaction (allergens) are applied to the skin. This is often done on the back using adhesive patches. These are left for a period of time, often 2 days. The skin is then checked for any reaction 2 to 4 days later.
Prick tests. Allergens are applied to the skin. The skin is pricked so the diluted allergen goes under the skin’s surface.
Intradermal tests. A small amount of diluted allergen is injected into the skin with a small, thin needle.
This test is used to diagnose skin cancer or skin disorders. A skin sample is removed and is checked under a microscope in a lab. Local anesthesia is injected to numb the area first. The sample may then be removed with a scalpel. For a shave biopsy, the skin sample may be removed with a razor blade. The sample is removed with a special tool (cylindrical punch) for a punch biopsy.
Skin, hair, or nails may be cultured to figure out which bacteria, fungi, or viruses may be causing the problem.