How do I keep mice out?

I have mice. I live in a single suburban home.It is built on a cement slab with no crawl space. I see them mainly on the first floor. They often hide under my dishwasher. I catch them on glue traps but it upsets me. I would be joyous if I knew how to keep them out. I can't get a cat my son is allergic.Any advice is appreciated.