Right now you don't know what is causing your rash, until you do take extra precautions with your grooming products. Even Dove Sensitive Skin Soap has over a dozen ingredients and most of the names are not simple to understand without an internet search, avoid them. I already recommended my safe, go to bar soap because it only has 2 ingredients. Grandma's Lye Soap for face and body in bar form. Please do not be alarmed seeing the ingredient lye. This soap only has 2 ingredients, lard and lye. During the soap making process, just like soap has been made for centuries the lye is converted into glycerin. Thus all that is contacting you is lard (moisturizing) and glycerin (moisturizing). This is all I use and keep at each sink in my house, shower and keep a bar in my purse. i also use this as a shampoo and it works great, but I also have soft water so I get lots of lather just washing once. If I don't have soft water will take 2 washings to get a lather. I order a 4 pack on Amazon. This soap is odor free and not drying to the skin. Best of all with all my allergies it is safe for me. Great for those with itchy scalp.
When my Grover's torso rash is active hot water hurts, also water pressure hurts. Thus I keep the volume low and the temp lukewarm. I am surprised heat doesn't feel bad on your rash.