I don’t suffer from the sitting problem as such but I’ve suffered from the "penis rubbing against underwear” problem for years, I would describe it as a burning sensation made worse by the slightest friction such as walking, walking always seems to make it worse, some days are worse than others but it is always present to some degree. As regards when I’m sitting the discomfort comes from any slight pressure from my clothes.

For a long time I just put vaseline on the glans as a barrier but it was just so messy and didn’t seem to help much, I have since tried many emollients but none of them really make much difference.

As regards meds, I was on antibiotics on and off for years for acne rosacea and a skin specialist who I was seeing about the acne rosacea had a look at my glans problem referred me to a penile eczema specialist, not that there was much evidence of eczema just the usual slight redness but anyway he reckoned it was related to my overall acne rosacea/eczema problems.
The urologist I saw at the penile eczema specialist clinic said there was no infection but that my skin was just very sensitive (she did a skin sensitivity test) and to try a range of antihistamines which are often prescribed for skin allergies but I didn't notice much difference apart from them making me drowsy, she also prescribed an anaesthetic ointment to help as she put it "retrain the nerve endings" I’m not sure I gave them much of a chance of working, I just didn’t get along with either and my doctor who specialises in STDs and UTIs didn't seem impressed with the idea anyway and said we had reached a point where it just seems to be in my head.

I sometimes do a lot of walking even though that makes the discomfort much worse and I’ve noticed in the shower after my walks that the corona (ridge of the glans) looks very inflamed. As I am circumcised there is obviously no protection for that part.

There have been very short periods and I mean a day or two when it has felt almost normal, on a couple of occasions on sunny days at the start of summer I have walked with negligible discomfort and after each of two hernia operations it felt fine for several days afterwards, I put it down to the anaesthetic and the painkillers which I was on for about a week following each op but when replicating the meds the problem remained, I suppose it could have been heavy anaesthetic still in my body post-op or recovery pain distracting?

I wish there was just one urologist/medical practitioner on the planet who could say "yes, I’ve seen that before and I know what to do about it” what a relief that would be.

For the record I also had chickenpox as a child.

Since I wrote the above I found this article which fits my condition / symptoms and also mentions the possible Rosacea connection.** the title is "Male genital dysaesthesia" (unable to post links yet)