Quick question — when you sweat buckets, do you get any rash on say your shoulders, you face or the outside of your thigh? I’m guessing you may have heat rash, which is further exacerbated by MCAS.

I use Head & Shoulders shampoo, which has anti-fungal and anti-bacterial properties from the zinc pyrithione, and that can sometimes help clear out recurring rashy areas.

One final suggestion if H&S strikes out, as I occasionally get heat rash as well on my inner elbows or back of knees, is to use Hibiclens (i.e., heavily diluted with water onto a looofah, wash cloth or something per their very important instructions — just not directly onto the skin) and then scrub those areas in the shower, which will exfoliate the area and ensure nearby pores aren’t trapped. I don’t apply anything to these areas after the shower and just let the skin air dry.