Folliculitis is a maddeningly itchy skin complaint which was probably, maybe, possibly brought on, in my case, by sweating for long periods in tight clothing. That was in 2018 when I was doing a lot of miles on the bike including RRtY and a Super Randonneur series. Cycling for up to 40 hours at a time may be good for your health but wearing the same clothes and not showering for that length of time possibly isn't.
It's made worse for me by being mis-diagnosed as eczema as the treatment for eczema can (and did) make folliculitis much worse. It can only be managed, not cured, so I'm stuck with it.
To experience it, imagine wearing a sandpaper vest stuffed with nettles, iron filings, toast crumbs and burnt currants. It's driving me nuts and it's making cycling very difficult as sweating in tight clothing makes it unbearable.
Not looking for sympathy but would like to hear if anyone else has it and how you're managing it. Currently, I'm using Hibiscrub as a soap and anti histamines for the itching. Neither seem to be doing much good.