I have several sabinos and that extra white gene causes sunburn. I've never had a horse with a dark nose sunburn so I'm going to assume that's not the issue.
Unless he's a grey, I can't see him changing colours as an older horse.
Has your vet ruled out allergies?
Coconut Oil is also really good for the skin.
Yeah I found it weird too but now that I think about it more, when the vet first came he said that it looked like a mild pigment change.. maybe his nose was changing color and the white made it prone to sunburn....
possible But I would really have it looked at maybe a new vet. If you let him out maybe put a fly mask that covers that area
I would not let him out in Full sun at all though
Well he's actually fairly young and he does itch it so something could have happened. He was indoors all day in his prior home and his dame is grey I can't imagine a gene for sensitive skin but I will have the vet come by this friday
Even a grey shouldn't sunburn like that unless there is pink skin under the hair. I have a grey and she sunburns on her pink nose. It is blistering and scaby so I tied her fly mask with the long nose on since she wont keep it on herself. I would probably start eliminating things to see if something is triggering a reaction.
IF it is sunburn, then I would say use infant sunscreen. It is uber strong, and it doesn't burn/taste bad/ melt off/ burn in eyeballs, and is safe to ingest. That is what I use. BUT this doesn't sound like sunburn, look into what everyone else is saying and maybe contact another vet.