I can only share my experiences with rashes, and tormenting itching. My cause is unknown, but may be similar to Grovers disease. I have tried numerous remedies to no avail. Tropicals, diet, cleansing products, too many to name. The only thing that helps is Triamcinolone cream, prescription applied 2-3 x daily. When I go into full blown body spread , the cream applied with cold wet wraps offers relief. Wet wraps are a white cotton t-shirt or leggings soaked in clean cold water...wrung out well, and put on over the cream. I'd then wear a robe over ,and wait about an hour. I have been prescribed meds to stop itching and get me to sleep.
Thankfully, I have not had anymore severe outbreaks for a few years. I do continue to get some spotty rashes, that the cream helps.
If you don't want to do all this, I suggest cold, very cold compresses. Also, I was told to take allergy pills, OTC.