Papulo-vesicular count for the rating of allergic patch test reactions. A simple technique based on polysulfide rubber replica.

Silicone rubber replica of patch test reactions were obtained from 12 patients with allergic contact dermatitis. 85 positive or doubtful reactions to allergens included in a standard battery were studied. The number of papulo-vesicles and sweat pores as seen in the replica were counted under a stereomicroscope. The papulo-vesicular count increased significantly in relation to clinical reading of the reactions of increasing strength. The number of sweat pores of positive reactions was decreased. This was probably due to cutaneous oedema with compression of sweat gland ducts. Papulo-vesicles are also consequences of the inflammatory oedema. The replica method was concluded to be a useful tool for the grading of allergic patch test reactions. It has the virtues of reproducibility, simplicity and low cost, and it can be evaluated under standardized laboratory conditions. Replica may also be the basis for more sophisticated methods of quantitation such as computer-aided image analysis.