When you apply THC to your skin, the molecule is too big to get into your bloodstream, so you will not get high at all, and don't need to worry that it would show up on any test (unless you ingest it). I have a topical cbd/thc oil and gel that I make and find that adding thc to the mix does help relieve pain more than cbd alone. Not sure why but that's what people have told me. Also, I've learned that the amount of both needs to be much higher to be effective. In either concoction there is about 2000 mg of cbd and 284 mg of thc per oz. I get cannabis from a friend who grows it and decarboxylate it myself (with a sous vide) to activate the thc.