• Wheal size area (mm2) of the immediate phase reaction. [ Time Frame: 30 minutes per subject ] [ Designated as safety issue: Yes ]
  

The skin testing procedure, based on the Nordic Guidelines is the reference method for the biological calibration of in-House Reference Preparations (IHRP). The method is not intended for routine testing of allergen extracts. The use of this procedure is the basis for the definition of biological activity units: "the activity of an allergen extract is 10,000 Biological Units (BU) per ml (10 HEP per ml), when the extract provokes an specific skin reaction in the median sensitive patient with a wheal of the same size as a wheal provoked by a positive reference solution consisting of histamine 54.3 mmol/l (for example histamine dihydrochloride 10 mg/ml), when both solutions are administrated using the same technique (prick testing) on at least 20 individuals who are clinically allergic and cutaneously reactive to the allergen concerned".