As someone who spent too many years handling neat lube additives and oils of every description, I would say ALWAYS treat these warnings seriously! I have seen a number of colleagues succumb to The Big C in their late '50s/early '60s. Coincidence? Maybe. Might they have died regardless? Yes perhaps but all chemicals, especially complex mixtures which are inherently chemically 'vague', are insidious little buggers and have nasty way of catching you out health-wise.
I ALWAYS wore latex gloves as a bare minimum, even for handling the notionally innocuous stuff like base oil (IMO there's nothing innocuous about Bright Stock!). Gloves are dirt cheap so use them.
Oh, and always work on the assumption that used oil is by far & away the nastiest of the nasty so protect yourself when it's oil change time.