Most violin varnishes are also medicines

The varnish used on violin bodies has so much influence on the tone that it is said to determine the tone of the instrument itself. In olden times, the varnish used by violin makers was a trade secret, and oddly enough most of them contained some medicine.
For example, the red varnish called dragon blood was used as a coagulant in Europe, the gold varnish of cambogia is a laxative, and the brown varnish of aloe is a tonic, while gambier is an oral stimulant. In addition, myrrh is a sedative, and benzoin is an expectorant and a cough suppressant. Black balsam and tolu balsam are used to treat dermatological diseases, beeswax is used to treat diarrhea and dysentery, and resins such as copal and dammar are used in healing ointments. Of course, the medicinal benefits of some of these ingredients seem to have been called into question.
(Source: Taken from The World of Musical Instruments published by Yomiuri Shimbun, and The Secret of Violin and Varnish, by Zoroku Murata)