I don't always find that various treatments touted by others (including doctors) work for me either, Rowan. As they say in many an ad "Your results may vary."

(Of course, I also don't know if the tea tree oil you used was comparable in formulation to what I use.)

I concur with your hooray for "evidence based assessment" in medicine. However, given the expense involved in doing well controlled double blind clinical tests on large, representative samples, many an effective herbal remedy will probably never have its effectiveness verified in that manner. Who's going to spend millions and millions of dollars to prove the effectiveness of something they can't patent? Or some plant extract that doesn't have a specific, constant chemical composition?   Sure, they can sometimes isolate particular active ingredients (e.g., ASA being originally derived from willow bark), but the derivative product is not always as effective or more so than the plant itself.