Why do your hands look chalky after eating an orange?

Answer 1

Yes, I've noticed this when I've peeled oranges too.
It's an accumlation of the wax that's used to coat the orange and the white part of the orange peel - albedo or pith.

Also, another effect is the orange oil in the skin is a natural solvent which dries out the skin... so you're getting the effect of having dried skin on the finger tips.

Answer 2

I have never had my hands look chalky after having eaten an orange, but that dosent mean that it dosent happen. maybe some scraps from the thick white layer under the peel are stuck to your hands; maybe it is just some dried juice on your hands; and maybe the evil christmas leprechauns freeze time every time you eat oranges and put chalk dust on your fingers in an effort to scare you into never eating their precious oranges again (for they use oranges and currency and also worship them as their sweet, seed-filled gods). I would suggest not eating oranges again until you call an exterminator for those pesky little orange worshipping leprechauns. or you could just wash your hands after you eat the oranges.

Answer 3

Probably the citric acid in the peel of the orange interacting with your skin.