128 Colour Change in the Human Histamine Wheal; a Sign of Desensitized Histamine Vasoconstrictory Receptors

Background The aim was to find the cause and consequences of a colour change in histamine wheals found after ordinary histamine skin prick tests (SPTs) (10 mg/mL). A rapid change to a darker red colour from the 18th and to the 20th minute has been demonstrated by using a digital image-processing technique called LYYN and ImageJ to yield numerical values.1