Replying to Essential? Oils

So I was looking around on the internet the other day trying to find pain relief for my knee from skiing that could be applied topically.
A shit ton of essential oils popped up and it got me wondering... hmmm are these really what every hippy and vegan mom make them out to be?
I used an oil on my face recommended for my skin last year by this promoter guy and it really ruined my face (Picture provided fuck oregano oil btw) so I was just wondering if any of you actually use them and what the hell for, or if you think they are a scam.
Just wondering.