Why is my dog shedding like crazy?

She is ten years old and has recently been scratching and shedding a ton. We bought a doggy brush and some medicine drops just in case it was lice, fleas, or ticks. We brushed her for a few minutes five or so times and the brush came out full every time. We didn't see any fleas or ticks or lice. Her skin didn't look or feel red and irritated. Does she need a good bath (hasn't ever had a bath before)? Should we take her to the vet? What should we do?