I use a trackball instead of a mouse, and I’m forever having to clean crud out of the thing. Well, once every few days anyway. The crud, of course, is dead skin cells. But why am I shedding so many that this happens?
could be a Mycobacterium leprae infection.
you are always shedding skin. you have found an undisturbed collection location.
it’s like belly button lint, it exists all over, that is just an undisturbed collection point.
Do you eat a lot of finger foods?
Apart from sandwiches, no.
Hansen’s Disease.
Is it all dead skin cells? Maybe it’s food, or general dust, the trackball is probably ‘grippy’ so will pick up anything on your fingers.
Great minds think alike.
And then there’s you two. 
At least it’s not lupus.
I find that hard to believe. It would be blood cells if it was coming off that fast !
Is your place dusty for some other reason ?
Is the computer directly under a window or something so the dust is coming from outside ?
Look, just put some honey on the table at the corner or something, for a day
and see how much dust is in it.
Mouse crud is mostly dust and desk crap congealed with skin oils. The oils are from your hand, the dust, while mostly skin cells, come from all over. Desk crap is bits of food (do you eat at your desk?) and other detritus.
:D:D
It’s never lupus.