Methodology of Open (Non-prick) Testing, Prick Testing, and Its Variants

Abstract

An introductory remark needs some explanation. When immunological contact urticaria {(ICU)} (see Sect. 10.1.2) or protein contact dermatitis {(PCD)} (see Sect. 10.2) is suspected, it is considered that prick testing is the “key” diagnostic tool to detect the incriminated allergens. Nevertheless, some dermatologists are reluctant to practise prick testing, particularly in cases of {ICU} when general symptoms have been mentioned by the patient (see Sect. 10.1.1). This attitude is fully justified, and in those cases, it is wise to start the investigation with an open test. A first approach is to use the open test as such (see Sect. 7.2); another way to test is to use a Chamber Test, similar to that recommended in the atopy patch test (see Chap. 9). The results of such investigations need to be carefully interpreted, as they can lead to false-positive reactions.