The Dermatology Service at Greenlane Clinical Centre provides a patch testing service.  Dermatologists apply patch tests to patients with dermatitis to find out whether their condition might be caused or aggravated by a contact allergy.  Many substances are able to be patch tested.  Nearly every patient has a standard series of patch tests applied to their skin, together with extra tests appropriate to the individual patient.  The patch tests are left in place on the skin for generally 2 days, after which they are removed and readings to detect positive reactions are performed.  Patch tests do not always explain the cause or find aggravating factors for dermatitis.  Patch tests are not the same as skin prick tests.  If you are having patch tests, ask your dermatologist to explain the tests.  Further information is available on www.dermnetnz.org