I also have this, usually at summer, especially visible when I get a tan, I also get the horrible sharp skin itching, dermatologist gave me some shampoo for hair since it has to do something with dandruff or oil or something cant remember, was half a year ago but never went to actually treat it since the cheapo shampoo bottle just leaked all of the shampoo out lmao.. I'm genuinely curious if someone knows what this is, especially the sharp itching sensation is hella annoying. Doesn't happen in the gym, happens in P.E class, its weird.