Okay I know this is a old thread but having experienced this in my early 2019 beginning Keto journey.
I have got to comment. This rash is due to starting Keto too fast. Keto should be begun slowly. Removing carbs slowly avoids this rash and the Keto flu. Learned this from Dr. Cywes. He suggest removing carbs slowly over days to not shock the body. Suddenly dropping carbs can really make a person sick. I know I dove off head first into Keto January 2019. Made me so sick I ended up in the ER. It’s not salt, it’s not electrolytes, it’s just moving to fast into Keto.
Now about the rash, it’s not going away until it wants to go away. I had it for 2 weeks. The only solution that I found was from a lady who had it really bad. I was desperate to try anything. She told me how,
Selsun Blue Shampoo, Its the thick blue smelly kind. IT WORKS! Use the original formula. Not the new brands, but the old one with the strong ingredients. Get in the shower, get your rash area wet. Then smear The Selsun Blue on and leave it on for a few minutes. It worked wonders, I did it a few times a day, once I just smeared it on without the shower
This was the only thing that gave me relief