My friend uses carburetor cleaner to clean off his hands because it will take basically anything off, from grease, tar, or even tree sap. Even though he has read the warnings that absortion through skin can cause central nervous system problems, he still does it. What could happen to him over the long term if he keeps doing this?
You’ll have to be more specific, since there are a number of formulations of carburetor cleaners. Here is the MSDS for one popular brand, STP Fuel Injector/Carburetor Cleaner: