I've been noticing recently when petting my cat that there are what feel like little scabs under his fur. They come loose and appear to be small tufts of hair held together by what looks like dry skin. Sometimes one will just be sticking out of his fur. They only seem to be around his head and neck. I've been curious for a few days now, but wasn't too worried, however today I noticed that one the top of his head had bled slightly. It's like if you pick a not yet healed scab, you know? What could be causing this? Do I need to take him to the vet?