Just recently bought a bottle of Reacta-Clean since I was running low on Tac-Up, anyway I noticed the warning "suspected of causing cancer" on the bottle of Reacta-Clean, never came across a warning like that on past bottles or on any other ball cleaners like Hook-It or C&D before...I do remember on an older bottle of Reacta-Clean saying denatured alcohol being an ingredient...so should I now be putting on a pair of nitrile gloves like a surgeon after every league set to use the cleaner? Sure my fellow bowler's will give me funny looks if I do that! lol
Honestly, all cleaners use some chemical that is harmful to humans, to one degree or another. Yes, every time you clean your ball you should use gloves. More than one of these "active' ingredients is known to have caused cancer by being absorbed thru human skin.
When I use Clean n Dull and Hook-it, I ALWAYS wear some kind of gloves. ALWAYS!
One chemical that makes Denatured Ethyl alcohol denatured is often methyl alcohol, which is very dangerous to humans. Nowadays, there are other denaturing chemicals, whose intent is to make the ethyl alcohol (the alcohol in all alcoholic drinks) undrinkable by humans. Methyl alcohol makes it poisonous.
Other additives that are used to denature Ethyl Alcohol include isopropyl alcohol, acetone, methyl ethyl ketone, methyl isobutyl ketone, and denatonium (denatonium benzoate -the most bitter chemical compound known).