How do I treat my kitten?

He has a flea (just one). At least I think it’s a flea. When we got him, we were told that they gave him one of the popular flea treatments, but it “didn’t work,” so they gave him a second and “that seemed to be working.” So that’s two flea treatments within a few weeks. I doubt he can have another right now, but what else can we do? Would a holistic treatment be ok?