I used to have that problem often, because I didn't want to spend the extra money for the bombs and Frontline. I thought I could just "clean" them away. Didn't work.
Ever since I bombed the house really good (every breathing thing out of the house for a few hours ) and started with the Frontline, we have had no problems. It's been a few years and I will never go without it again.
The bombs are much safer than they used to be, I suppose. Poison is poison, though, read the instructions. And Frontline every month May-October.
The teeny tiny white spiders in my house are a whole 'nother thing. I can't find a way to get rid of them. But they don't bite, like fleas.