Very dry and flaky skin...

[SnowBP]

Do you have a picture of him showing what concerns you?

It would be hard to capture on a photo. You notice it more by touch.

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I haven't had Nagini for very long and am by no means an expert, but I have noticed that the further he gets from one shed and the closer he gets to another, his skin, especially along his stomach, starts to flake, and gives the appearance of dry skin much like you're saying. It's entirely possible that yours is just going into a Shed cycle.

Could be that it's been so long since a shed that his skin is getting this way. Don't know what is taking so long.