More positive patch test reactions with larger test chambers? Results from a study group of the German Contact Dermatitis Research Group (DKG).

Test chambers of various sizes are commercially available for patch testing. Therefore, we asked the question whether the size of patch test chambers may affect allergic patch test reactions. A total of 495 patients were double tested synchronously with small and large Finn Chambers containing standard preparations of fragrance mix, wool wax alcohols, Kathon CG and formaldehyde. Double tests in 217 patients who had reacted with at least 1 allergic, questionable, or irritant reaction to 1 of these allergens were statistically evaluated. For each of the 4 allergens, a significantly higher number of stronger reactions was seen with the large chambers as compared to the small ones. It is concluded that large test chambers may be useful for detection of weak sensitizations to particular contact allergens.