Heat Rash

[Eve]

I've had what I assume is a heat type rash at the beginning of my arms at the back of my armpits on both sides, assume it's a heat type rash with it being round where the skin is between the back of my arm and back and round part of my bra and with the warm weather. It's like a row of little spots both sides, quite irritated and itchy and won't go away.

The skin also feels wrinkly/tethered round them which panicked me a bit after being told skin tethering was a bad thing when I had a breast lump scare some years ago and had some tethering. This is by my armpit but not right under or boob side, it's more towards my back.

Anyone have any ideas as to what might shift them, or at least calm it down, as they're hard to leave be as they irritate.