I diffuse a thieves blend if someone in our house is sick. Normally I just diffuse lemon or a citrus blend to freshen the air and kill germs. I save thieves for actual illness or if we’ve been around someone sick. I buy all my oils from Hopewell essential oils.com They have great quality oils at a fraction of the price of the MLM companies. :)

Angela S, I know what you mean. Somebody has to pay for those MLM companies and it's the consumers!

Probably for any of the oils you find for sale on Amazon, the company can be found and researched a bit. I ordered from Mountain Rose Herbs a few years ago, then visited the store in Eugene Oregon when I was out there last year. They have good quality and seem to be very customer oriented.
However, for me, Thieves is a little overpowering. I have some Young Living Thieves that I hesitate to use much because it is so strong. Different companies have their own mix of Thieves. I think the ingredients are kind of flexible, as many oils have the same qualities.

Edens Garden also sells good oils and blends at better prices.

Someone gifted me a bottle...I cannot tell you where it is. That is my "opinion". For me, It was not important. I appreciated the gift...just never used it. I love hand lotions. : D