Wintergreen is not only dangerous when in ingested, it is chemically very similar to aspirin only far more potent and even topically can be a blood thinner. Another poster (I am sorry I do not recall if it was here or elsewhere) shared that they used wintergreen in a pain relief balm for arthritis and very nearly killed the user. I have no idea what "safe" levels would be, but there are a lot of other scents I would choose over wintergreen for that very reason. If you do not know how much is too much, I would say do NOT risk it!