Every winter since I was a kid, I get Keratosis pilaris [0] on my inner upper arms, which is a bit of a nuisance. After the first day of spring sun in a T-Shirt, it disappears completely within days.

[0] https://en.wikipedia.org/wiki/Keratosis_pilaris

Oh, I've always thought it's just a lack of sweating causing your dead skins to grow over the pores, didn't realize that it's actually a mysterious medical condition?

Have you tried irradiating with near infrared light in the winter? Eg with a cheap CCTV IR light off aliexpress.