What Causes The Boils On My Skin?

I was wondering I seem to get one or two boils a week usually on my arms I am working as an auto mechanic and was wondering whether or not with the potential for me cutting or scrapping my arms and getting transmission, power steering, coolant, engine oil or brake fluid's in them could be causing the boils. I have been tested for every immune disease and everything is normal but the doctor just seems to believe that it maybe genetic but no one else in my family suffers from them and it just started when I change jobs from sitting behind a desk to becoming a mechanic