• Open test ("open test") is to apply the allergen skin territory (e.g. 5 x 5 cm) without occlusion. The locations of choice are the flexion of the forearm, the crook of the elbow face or the face of the arm extension.

The use of this test is interesting in case of suspicion of a contact urticarial reaction (reading in the 20th minute, for example the Peru Balsam ave) or even when it skips the irritating power to the product testing. This technique of unoccluded prevents possible necrosis of the site tested, if the tested product is caustic.

The "semi-open" test is a useful variant, when testing products whose chemical composition is not known.

The method is to apply a product open on a limited area of the integument: if it is a liquid (aqueous solution, oil, etc.) the application of two or three drops on a zone of + or - 1 cm2 is recommended. After a few minutes, the tested area is covered by a strip of adhesive tape Micropore ™, which provides the semi-occlusion and the identification of the tested website.

This method is very useful in investigations of industrial Dermatology.

• Iterative open tests ('Roat Tests')
A very useful test, to determine the appropriateness of a positive patch test to a specific allergen, is of iterative applications of the same allergen, open, concentration and in a nearby vehicle of its use in everyday life.

This is the open test or ROAT test (Repeated Open Application Test) Hannuksela. In practice, applying the allergen twice per day on a surface clear of the integument (e.g. 5 x 5 cm) or on the face of flexion of the forearm, either on the face of the extension of the arm, or in the scapular region. We stop the applications in case of positivity of the test.

If at the end of 14 successive applications, the test is negative, it puts an end to the test and is considered the test as negative. The cooperation of the patient is paramount.

• In-use tests ("Use Test" or "In Use Test")
The use test is to apply a finished offending the cutaneous territory where he is supposed to have previously caused eczema. This application is done in conditions quite similar to those for use in everyday life.

For example, if there is suspicion of allergenicity of used cleaning to bare hands, we recommend that you ask about the presumed allergic reuse according to the terms and conditions of employment which are usual.

A suspected allergic to a rubber glove reaction can be checked in fine by the port reiterated this glove, which must lead to the reappearance of eczema. The active cooperation of the patient is essential.