ABSTRACT
A drop of the allergen extract and controls (positive (histamine 1-10 mg/ml) and negative (saline or diluent)) are placed on the skin of the volar aspect of the forearm
and punctured by means of a 1 mm sterile lancet or a 25 gauge sterile hypodermic needle. The excess solution is absorbed after 30 seconds with an absorbent tissue and the reaction is evaluated after 15-20 minutes. The response is measured as the largest diameter of the wheal and its orthogonal diameter. In the absence of a reaction to the negative control, a reaction of 3 3 mm is considered as a positive response. It has been shown that a true wheal diameter of 3 mm represents 10
Figure 1.1 Skin prick test for standard panel of airborne allergens. Note positive responses (wheals) to house dust mite (HDM) and cat. : positive control (histamine); : negative control (saline).
