Rosin (colophony) and zinc oxide in adhesive bandages. An appropriate combination for rosin-sensitive patients?

Adhesives and bandages containing zinc oxide (ZnO) and rosin are often used for treatment of ulcers. The aim of this work was to study a possible inhibitory effect of ZnO on the elicitation of allergic contact reactions to rosin and to determine whether such an effect might be due to the formation of zinc resinates. Patch testing in rosin-sensitive patients was performed with mixes of ZnO and rosin. The eliciting capacities of one mix in which zinc resinates might be formed and another mix in which the formation of zinc resinates was prevented, were compared to the eliciting capacity of rosin alone. If a reduction of the allergic response was observed for the mix in which zinc resinates might form and if no reduction was observed for the mix in which formation of zinc resinates was prevented, this would support the hypothesis that the reduction in eliciting capacity was due to formation of zinc resinates. However, we could not see any difference in eliciting capacity when comparing the 2 mixes with a test preparation of rosin. Commercial adhesives (bandages) containing ZnO and rosin were patch tested in 7 rosin-sensitive patients. The concentration of abietic acid in the adhesives was determined with HPLC. Abietic acid was detected in all but one of those declared to contain rosin. The patients reacted to the adhesives in which abietic acid was detected. For rosin-sensitive persons, the addition of ZnO to rosin-containing adhesives cannot be regarded as an appropriate measure to inhibit the elicitation of allergic reactions.