I know you asked about skin absorption but the other very important reason for not using gasoline in a parts washer is the flash point. Gasoline has a flash point of -40 degrees while kerosene has a flash point of about 110 degrees. The gasoline can be ignited from a nearby ignition source at most any temperature likely to be in your shop while the kerosene would have to be heated to over 110 degrees for the same nearby ignition source to ignite it.
