Did you ever find a solution to your problem?
I think I have the same problem.
Thanks for the input. I had to do SOMETHING about this, so I got out the Bag Balm (a veterinary...but OTC, antiseptic salve I use all the time for dry, cracked skin), slathered it on the buttock and into the anal crevasse, and put on a pair of snug-fitting boxer briefs to protect my clothing (and most anything else) from getting the ointment on it. I really had to force myself to NOT SCRATCH the itching, but after a couple days of keeping the skin ointmented 24/7, the irritation went down. While I need to do this until I'm certain it's gone, the bumps are gone, no new red spots, and the worst spot where I tore the skin has scabbed and is healing.
If I had to scratch that itch, I normally did so by rubbing the area in the shower with a washcloth and soap and water so I'd not keep tearing the skin with my fingernails.
Normally, when lounging about the house, I just wear a pair of old athletic shorts, w/o undergarments (comfort issue for me). Out of habit, I just wear the same shorts all week. I suspect that's how the irritation got started...fabric soiled with body oils and dirt constantly rubbing against the skin.
Time to buy more shorts.
From the symptoms it looks like folliculitis due to irritated hair follicles due to continuous sitting. Keep the area clean and apply some topical antiseptics. Also wear loose-fitting cotton clothing and use an antibacterial soap or mild soap like dove. Avoid any kind of cosmetics. Topical antibiotics such as mupirocin or Neosporin can be applied but if the symptoms are severe then get an evaluation done from a dermatologist. You may need oral antibiotics.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.