Not Medical Advice: Vicks VapoRub is typically applied to the throat and chest but applying it on your upper lip does not pose any health threat. No reported incident of medical emergencies has been heard by doing so.
A study published in the Journal Pediatrics, aimed to compare the efficacy between Vapor Rub and Petroleum Jelly, even allowed parents to apply Vicks between their upper lip and nose before opening their child's treatment. Doing this, they smelled the vapor rub regardless of which treatment they then gave their child.
Vicks VapoRub should only be used on children ages two years and up. Do not use Vicks VapoRub beyond the expiration date on the package.
You should not heat or microwave the product. Do not add Vicks VapoRub to hot water or any container where heating water. Doing so may cause splattering and result in burns.
For more info on how to use the product properly, see Vicks.com's Vicks VapoRub FAQ page.