The "Patch" test is an epicutaneous diagnostic test using standardized haptenс. The test is performed by the application of haptenс (allergens) in small chambers mounted on patches that are placed on the patient's skin. In sensitized individuals, this immune response leads to allergic contact eczema limited to the site of application on the patient's skin (positive patch test reaction).
Allergens are grouped in series. Typical screening is performed by testing with a "Baseline series" (sometimes called a standard series). The standard series contain a selection of common high-prevalence allergens in a specific area, while the special series contain allergens that have a high prevalence in certain professions. The combination of series should be determined by the patient's specific history.
To ensure that the allergen will remain in direct skin contact for the required time (48 hours), and to create a standardized controlled response, a patch test is required. The "patch test" patch is made up of a group of chambers mounted on a self-adhesive tape. The purpose of the chambers is to provide a specific area in which the skin is exposed to allergens during the test.
The test includes a number of scheduled patient visits within one week. After the test is applied on Day 0, two or three visits are needed. The primary reading should be done within 48 hours of removing the patches. A delayed allergic response should be performed after 72 hours and / or one week after the initial administration of the allergens.
Requirements for conducting epicutaneous testing:
- Discontinuation of systemic anti-allergic drug therapy for at least 2 weeks prior to the day of testing. Failure to comply with this condition usually results in a false negative result - a lack of reaction to allergens.
- With an active disease, it is necessary to wait for improvement in the condition of the patient. Otherwise, a false-positive result may be observed for most or all allergens.
Recommendations during the test period:
- Do not expose to intense sun (tanning beds) a few weeks before testing and until the rash disappears on your skin if the test is positive.
- Stop taking anti-allergic drugs at least 2 weeks before testing.
- Keep your back dry until results are read, do not bathe, do not swim, avoid excessive sweating and physical stress.
- Do not rub your back and do not exercise because the patch can be shifted or peeled off.