Apply one drop for each allergen extract to be tested, maintaining a minimum distance of 3 cm between drops on the volar part of the patient’s forearm (5 cm from wrist and 3 cm from the antecubital fossa) |
Apply pressure, through a sterile, disposable lancet, to each single allergen, pricking to a depth of 1 mm for each drop, perpendicular to the skin’s surface |
Hold for about 3 s with moderate pressure without moving the hand or turning to avoid bleeding |
Carefully remove the allergen solution with blotting paper |
The same procedure is to be followed to test histamine (10 mg/ml) as a positive control and physiological glycerine as a negative control |
Reading of the results: after 15 min from the performance of the test |
Interpretation of the test: a positive result is defined by the appearance of a wheal of at least 3 mm in average diameter. Responses to histamine and the negative control should be carefully considered. The latter verifies that the patient does not suffer from dermographism and the former demonstrates a “normal response” to histamine (with no negative interference from drugs or other conditions, such as hypo-reactivity of the skin) |