The SPTs were performed according to the standardized
techniques [29]. All SPTs included positive (10 mg/ml histamine
hydrochloride, Stallergenes, France) and negative
controls (phenylated glycerol-saline, Stallergenes,
France). The results were assessed after 15 min. Positive
reaction was defined as a wheal diameter of at least 3 mm
in the absence of reaction to the diluent and in the presence
of a positive reaction to histamine.