itchy from my bfs dog ???

I've been with my bf for 3 years now & I used to sleep over at his house, no problem. But within the past year I got a big rash on my butt & upper thighs. I didn't know what it was & I couldn't stop scratching so I went to the doctor & he prescribed me cream (which I ran out of :(). It went away but every so often I start to get itchy again & rashes will appear mostly on my thighs now. Yesterday, I started to get SO itchy all over my legs (thighs to ankles) and am still itchy today. I put cream on it that I know helps, but not consistently so it's still itching a bit. I finally figured out that it's his dog, who likes to jump on everyone's beds & roll around it in, and shedding so much hair every where he goes. I told my bf about it & he said he'll make sure his dog stays off his bed but idk why I'm still itchy if he hasn't been on his bed. I hate having to cover my legs anytime I want to lie down in his bed just so I don't get itchy. I always have him wash his bed sheets before I come over & I think that helps. I'm just not sure what the dog might have (he has skin issues that I think is mange but my bfs mom refuses to believe it) that's making me itchy??? It's weird though because I'm not "allergic" to my dogs or any dogs at all!
 It makes me have bad skin from itching, sometimes leaves scars, & is just plain annoying! What could it be & what else can I do l??? Please help!