Brian Mailman wrote...

He mentioned being a gay male, so odds are his rash is HIV-related.

I had all kinds of rashes for decades.  It has to do with your body
being hyper-reactive, due to the fat in your diet.  You need to get a
fatty acid out of your cells called arachidonic acid, and let your body
make its own, called the Mead acid.  It will take a couple of years,
but you should see improvement within weeks.  You can eat whole milk
dairy (though avoid addivitves like carrageenan and also homogenized
products), boiled eggs (1 or 2 a day), shellfish (boiled), fish with
very little fat content (boiled or in a stew), dark chocolate, fruit,
bread with very little fat content (like French baguette), coconut
products, and a level teaspoon of nutritional yeast each day should
help.  You also may be deficient in some vitamins and minerals, but you
would need to test for that, and even then it may be difficult to
determine.  You can get some B complex powder and let tiny amounts
dissolve under your toungue a few times a day.  Also, you may need a
stomach acid and pepsin supplement.  Do you have acid reflux/heartburn
problems?  If you hardly ever do, you probably need the
supplementation.  You can use vinegar at first, to test to see if you
do.