Repeat patch test/testing for high sensitisation potential
The repeat patch test is characterised by three standard patch tests performed with the same product within 7 weeks. The aim of the study is therefore not only to detect primary skin irritation caused by the test product and/or pre-existing sensitisation to the test product, but also to exclude an increased sensitisation potential of a product. If the first two applications (initial patch test and a second one following a 2-week break) lead to sensitisation, this becomes apparent in the third patch test (after a total of 7 weeks) and a reaction occurs. Accordingly, positive skin reactions which occur only in the third patch test provide information about the sensitisation potential of the product being tested. If there is no irritation from any of the three tests, an overall low sensitisation potential can reasonably be assumed.