Wikipedia
Synthol
Synthol is a supplement available in France since 1920. It was developed by Maurice Bunau-Varilla, a prominent newspaper publisher of the early twentieth century. He promoted it as a cure-all tonic.
The formula consists of chloral hydrate, menthol, veratrol, resorcinol and salicylic acid. Sold mainly as a mouthwash in a distinctive black carton, it is also packaged as a gel and spray for the treatment of muscular pain(s).