Intracutaneous Test Reactions to Tuberculin Containing Merthiolate as a Preservative

Abstract

Merthiolate (thimerosal) gives a high frequency of positive reactions when tested epicutaneously and intracutaneously in young adults. To Swedish old tuberculin (OT) merthiolate is added as a preservative. The reactions to intracutaneously injected OT, merthiolate and purified protein derivate (PPD) has been compared in 412 healthy young adults. A positive reaction to merthiolate was recorded in 15%. It was found that merthiolate influenced the reactions in 63 of the 163 positive OT tests. Consequently, merthiolate should not be added to intracutaneous test solutions, since this additive may interfere with the evaluation of positive reactions.