How do I get rid of A LOT of house flies without harsh chemicals.?

I had to leave the house yesterday for a few hours and while I was gone our three dogs voted for the Bull Mastiff to knock one door open instead of using the doggy door. There are now HUNDREDS of flies in my house. Last night I hung two fly strips in the bathroom and left the light on to attract them. They were COVERED this morning. There is still a curtain of flies in my house whenever you walk in a room. How can I get rid of them safely - I have three dogs and a 6 1/2 yr old. I do NOT want to use harsh chemicals, my arms are tired from swatting flies, and I have gone through 2 more fly strips - now the little cretins are starting to avoid the strips. PLEASE HELP!!!!!!!!!!!