Interesting that these articles agree with my own unpublished work from the late 60s when I was working in the Bacteriology Dept of the MAFF Central Veterinary Laboratory. I did the work with Dr George Slavin who was a renowned expert in the field of disinfectants. My favourite quotation from him was that "The most unscientific person is the professional scientist, and the most scientific is a baby in its cot."
I know the focus is on alcohol concentration, but just a quick warning about Tea Tree Oil & Lavender Oil. They are in a class of substances that activate the same receptors as estrogen. Just as men and women create and use both testosterone & estrogen in our bodies, we have receptors for both. Plant oils such as these can cause endocrine disorders such as gynecomastia. So be careful with the concentrations & application. Probably not much of an issue for older adults but I worry about kids, especially since hand sanitizer is used so often.