Hi My Son Has Patches Of Rash Like On His

hi my son has patches of rash like on his hand arms and to of foot. first it was just on back of hands, he has been changing car oil on his job for over 3 years, he thought it comes from removing the hot oil from customers care. I just notice that these patches are on his arms and legs. what can I use to get his skin better or do he needs to go see a skin doctor?