Strange “rash” whenever I’m ill

[u/TobyPearcepng]

25M

So whenever I get a cold, flu, Covid etc. I get a very strange rash on my hands and feet. The rash doesn’t hurt, nor does it itch or anything of the kind. It is a purely aesthetic problem, I’m not concerned by the aesthetics of it but I would like to know what exactly is causing this.

Thank you! Pictures in comments

[u/TobyPearcepng]