The most widely used patch test material consists of strips of paper tape onto which are fixed 8 mm diameter aluminum discs. A small amount of allergen is placed within these discs, discs, covering slightly more than one-half the diameter of the disc providing a dose approximately 17 ul. Apply the patch to the upper or mid back, which must be free of dermatitis and devoid of hair. If shaving is necessary, it should be done only with an electric razor. One additional reading at 72 or 96 hours, and occasionally at one week.
Tiny vesicles are present over the surface.
Emergency resuscitation equipment should be available. Contact urticaria should first be evaluated with an open test on sites adjacent to active dermatitis. Chemical analysis of environmental materials to determine if they contain a substance to which the patient is patch-test positive. The most commonly employed of these is the dimethylglyoxime test for nickel. C. Inappropriate initial assessment methods 1.