When I first saw your question I noticed that others had already replied to you. However, reading again (and the Aromaweb link
@Mobjack Bay posted is great, that site is really thoughtfully put together!) you can also check out
THIS link, that adresses wintergreen specifically.
Tisserand is one (
to me he is THE one) that has a very balanced view about the essential oils available out there, in my book -
(both literally and figuratively speaking, as I have his Essential oil safety book, lol)
Also - be sure to read the comment field in the wintergreen link as he answers some concerns from people.
Some things he mentions in his article is:
Even if you are going to use it in a soap I would at least write a warning on the label, so that people can take that warning into account if you decide to give it away/sell or in other ways share your soaps containing Wintergreen.
People don`t imagine that things like essential oils can affect the medications they use, but they can. Even though a soap is a wash off product at least you can perhaps let people know about any contraindications so they can choose what to do?
Remember, not everyone wish to disclose their medical issues, no matter how small, so you might not know , even though you may know them well.
On a personal note - yes, it will affect trace to your soap. If you use it at 2% it may not be a big reaction, or an instant one, but it will at one point thicken your soap up, so just keep that in the back of your head when you work with it.
Since I have several familymembers that use bloodthinners and other medications I am not using this oil in my soap anymore. But - I do use it in a painrelieving balm as it has pain relieving properties even at tiny ammounts added.