How to induce a blister before biopsy for epidermolysis bullosa

(A) Rub the normal skin with twisting movements of a pencil eraser for a few seconds and repeat. The skin should not peel. Recheck the area intermittently for redness and vesiculation before performing the biopsy.
(B) This is the degree of redness and vesiculation needed before taking the 3 mm punch biopsy for immunofluorescence mapping in the vesiculated area. The 2 mm punch biopsy for electron microscopy may be taken from this area also.