R.C is one of the oils that comes in the premium starter kit, and I think in our house it is one of the most commonly used oil. It really helps with chest or sinus congestion. I put it on my chest, back and feet anytime I am congested and fighting off a cough or cold, as well as diffuse it. It also works great if you put a few drops along the side of your shower and then have a hot shower or you can add it to your bath with some Epson salts.
R.C essential oil
Common Scents Living 