A bit of history. I am very allergic to rats and sheep.
I know about the rat allergy because I had a pet rat, that nearly killed me. As my allergy worsened, I actually stopped breathing one day when I tried to play with her.
I know about the sheep allergy because I spent 2 weeks on a sheep farm in Wales while I was an undergrad. I also know about the sheep allergy because I also react to wool, cashmere, merino, etc. (I even swell if lamb meat or mutton touches my bare skin.)
If I come too close to either rats or wool, I tend to get very red, my face swells a bit, and I wheeze.
I made an attempt to go up into our attic, and all of these things happened.
So this tells us that there is either wool, or rats in the attic.
It could be wool insulation. I wouldn't be surprised if the insulation was never touched up there.
But then again, when we came to look at the house the first time, our friend poked his head up into the attic and saw a raccoon (who has since moved into the attic of the house next door), so a rat could have moved in.
Either one is not good.