Does anyone know if Dr.'s can test the fluid in a blister to find out what it is?

So I posted on Sunday that DD had blisters on the back side of her left hand. I brought her to the dr. Monday and he ruled out chicken pox and coxsakie because of the way the blisters have formed on the red patches ( it is linear).
The blisters have now moved up arm but is not spreading to any other body parts. Then tonight she went to bed with a fever of 101.7. She still seems irritable.
I tried looking online to see images and I can't seem to find anything that looks like it. The images that I saw of coxsakie on Sunday that were posted were kind of distant and I found one closer up and it doesn't look like that.
The Dr. diagnosed her with contact dermatitis but I am thinking it is something more now that she has a fever but I don't know what. I thought maybe impetigo but it's not it either.
I can't get a good picture but it looks like when you burn yourself and you get a blister but picture that blister smaller and a few of them on one small red patch.
I am going to call the ped. again tomorrow and see what he says but I just thought maybe someone knows of something else in the mean time.

Re: Does anyone know if Dr.'s can test the fluid in a blister to find out what it is?

I would take DD to a pediatric dermatologist who can use a razor and scrape one of them to get a culture. While pg with DS I got these strange blisters on my chest and they ended up being from stress. I was so stressed at work while pg with other complications that my body broke out in hives.