My cat has small, scabby bumps all over, under her fur. any ideas as to what this might be?

It could be anything from mange to kitty acne. I hate saying it as much as you hate hearing it, but it might be time for a vet's intervention.

Has she had fleas recently or have them now? My cats got fleas last summer due to the heat and our whole house had to be sprayed even though I flea them monthly and then a few months later I started to notice small scabs on Pixies body and she was itching but I checked for fleas and she had none so I put it down to her and her brother being to rough playing. But a few weeks later they had spread all over her body and it turned out she had an allergic reaction to the fleas she had in the summer. One simple allergy injection and a week later she was scab free and actually a lot more playful!

my cat had that a while ago and it ended up being because he fought with other cats, but i don't know if that could be it