An outbreak of itchy red bumps all over my back!

Hi all. I am on day 9 1/2 out of 21 of my water only fast. I just noticed a really nasty rash spreading over my back and it itches a lot. I also fasted about 6 months ago for 14 days and I got the exact same rash after about day 10 and ended up not finishing the fast (it was supposed to go for 21 days too but I quit on the 14th day because I was worried about the rash). Can anyone tell me what this is? I want to make sure it's not dangerous like a liver problem or something like that. Any advice would be helpful!