@scoop They are most likely medical grade essential oils. All of the literature on nebulizing tea tree oil talks about the insolubility in water, and when it is used clinically, they use a specially prepared solution where the particles have been physically broken down to be small enough to penetrate. So my concern is whether the oils actually penetrate the lungs, or just coat the inside of the neb cup.

I have used neither tea tree nor eucalyptus oil in a nebulizer because I refuse to put anything "foreign" in my damaged lungs except unless the supervision of my pulmo. The other concern I have is how to avoid contamination of the oil bottles once opened - most of what we nebulize comes out of sterile, single use vials.

That said, I am a big user of essential oils, and I am very careful handling all my oils, keeping them in a special dark container and cool temps, and not letting anyone else touch them. I blend them in a fully cleaned kitchen using sanitized bottles, vials, and tools. I sometimes blend tea tree, eucalyptus and plus a few other oils with a neutral oil in a tiny bottle, then drip a few drops on my finger and rub it UNDER my nose to inhale. It is helpful when used in conjunction with my meds if I have congestion or wheezy lungs.