67th Tigers
Banned
For very good reasons.
The prevalent theory was that "miasma" (bad smells) were the source of infection. It had recently been disproved (in 1854) in London, Pasteur disproved the spontaneous generation variant of germ theory in 1857.
Germ theory had gained acceptance in Britain by the 1860's, and Lister would use the theory to develop antiseptic theory in 1865, which was an expression of practice that had developed over the previous 5 years (mostly in Britain and France).
Certainly, British Military Field Hospitals had adopted antiseptic techniques around this time (essentially dowsing stuff in Phenol or similar), although I don't know if the Union had.