I read tobacco leaves can be used to prevent leech bites. I'm unable to find tobacco leaves so can I use cigarettes instead?
Q: Would it work?
A: Probably, tobacco is toxic to Leeches, but the problem with rubbing cigarette tobacco all over your legs is you will also absorb all of the manufactured additives and toxins put into the cigarette tobacco. You'd be better off using chewing tobacco.
Tobacco accelerates coagulation and was used for its medicinal properties in the past. The leaves are still used today by some cattle ranchers to heal bruises on cows and stop bleeds. If you want to order just the leaves you can do so online: https://www.leafonly.com/
Leeches inject an anticoagulant when they bite in order to prevent the blood from clotting so they can get a steady stream while they suck, and easily detach. It's for this reason that leech bites tend to bleed for a long time.
I suspect it's the hypercoagulation provided by tobacco that makes it toxic to leeches, but before you start rubbing the stuff all over your body, I recommend you check out Leech socks:
They are much more effective than repellant, and won't introduce anything into your blood stream.
Related: How do I avoid leeches?
There's plenty of anecdotal evidence that suggests tobacco is toxic for leeches. However, I couldn't find any sources that mention why (thought I found a promising paper in Arabic, which I can't read, and the English summary was insufficient).
So I'm risking a bit of a wild guess here and assume that the compound that makes it toxic to leeches is nicotine, which is known to be an insecticide (and was widely used in the past as such, according to Wikipedia). And as far as I know, processed tobacco (used in cigarettes) has pretty much the same nicotine as the natural tobacco leaves. If anything, a lot of other chemicals are added.
Seeing as you're unable to find tobacco leaves anyway, I'd suggest you go for it and try using cigarettes.