patch test

patch test

n.

A test for allergic sensitivity in which a suspected allergen is applied to the skin on a small surgical pad for a period of time to determine if an allergic response is present.

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Patch test

A skin test that is done to identify allergens. A suspected substance is applied to the skin. After 24-48 hours, if the area is red and swollen, the test is positive for that substance. If no reaction occurs, another substance is applied. This is continued until the patient experiences an allergic reaction where the irritant was applied to the skin.

Mentioned in: Dermatitis, Skin Lesions

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patch test,

a skin test for identifying allergens, especially those causing contact dermatitis. The suspected substance (food, pollen, animal fur) is applied to an adhesive patch that is placed on the patient's skin. Another patch, with nothing on it, serves as a control. After a certain period (usually 24 to 48 hours) both patches are removed. If the skin under the suspect patch is red and swollen and the skin under the control area is not, the test result is said to be positive, and the person is probably allergic to that substance. Compare radioallergosorbent test.

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patch test,

n a skin test for identifying allergens, especially those causing contact dermatitis.

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patch

a small area differing from the rest of a surface.

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patch grafting

see patch graft.

serosal patch

creation of an adhesion between serosal surfaces in order to cover a defect or perforation of bowel, often accomplished by suturing another section of bowel over the area.

patch test

a test of delayed type hypersensitivity in the skin used in the diagnosis of allergic contact dermatitis. The substance suspected of being the cause is applied to the skin, either under a dressing (closed patch test) or without a covering (open patch test). The site is examined at regular intervals for up to 5 days to detect any inflammatory reaction of the skin.

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patch test

Allergy skin test, contact dermatitis skin test, patch skin test Immunology An epicutaneous test of contact-type–delayed hypersensitivity, which consists of applying a patch with a low dose of an allergen–antigen to an unexposed area of the skin, usually the back, and observing the site 1-2 days later; the most common sensitizing haptens in North America are poison ivy–Toxicodendron radicans, nickel, chromate, paraphenylenediamine–a dye constituent, ethylenediamine–a solvent and emulsifier, local anesthetics–eg, benzocaine, rubber, neomycin, and others; PT materials have been standardized and are available commercially, either as individual allergens, or as batteries of allergens, including those for specific occupations–eg, hairdressers, printers, and others; incorrect PT results are common in the form of false-positives, due to too high concentration of allergens in the patches, misinterpretation of irritant reactions, and generalized erythema of the skin testing site; false-negative results are linked to technical errors and failure to simulate the 'real-world' situation in which the person is exposed to the allergen