So they did a skin scrape and found 2 mites, which is enough for the vet to decide to treat her for demodectic mange. Basically these mites live on dogs all the time, but sometimes (like after a course of antibiotics or an illness) the dog's immunity can be reduced. Oddly First hasn't been ill or had antibiotics. However the vet said that sometimes just age can be a factor. First will be 8 in March. Anyway, she's getting Advantage Duo for that.
This time around her vaccinations also included Lepto, which she'll need a booster for in 2 weeks. Doop de doo, more needles. But since lepto is one of the few things that can be passed to people and First goes on farms and is likely to be going on more soon, I reckon fair enough.
Other than that she is, apparently, a picture of good health. And she's busy charming pats out of all and sundry in the clinic.
I needn't have worried.