Calling all dog lovers...

This red mark has appeared on Millie's inner leg. I suspect she's been a bit itchy and has broken a few blood vessels, resulting in a red blotch. I will of course keep an eye on it. I know there are loads of dog lovers out there in Blipland. Anyone any ideas? It doesn't seem to be painful; is not open, crusty or weeping; is not a birthmark; doesn't seem to bother her.