Used to get this a lot in my last job too, we had another nickname for it..
It’s sweat rash, I tried all sorts and the only thing that was guaranteed to prevent it...... seriously, a quick spray of antiperspirant in the canyon of Uranus.
The amount of times I walked out of work bow-legged and in excruciating pain in my last job was unreal but once I started using antiperspirant I’ve never had it since. Make sure you’re not sore at the time though.