Skin tests may be done to diagnose 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.
Allergy Testing. Skin tests for allergies include:
Patch testing. Patch tests are used to help diagnose skin allergies leading to contact dermatitis. Possible allergens are applied to the skin (usually the back) with adhesive patches. They are left for a period of time, usually 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 allergen goes under the skin’s surface.
Intradermal tests. A small amount of allergen is injected into the skin with a needle.
Skin biopsy. This test is used to diagnose skin cancer or skin disorders. A skin sample is removed and checked 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.
Culture. Skin, hair, or nails may be cultured to find bacteria, fungi, or viruses.
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