breaking out in a rash

I've been alternating between fasting and eating under 200 calories a day for the last two weeks. After the first few days I started breaking out in a rash. There are spots on my arms, it's all over my neck, and especially bad on my chest. It seems to be getting worse every day, and it's now spreading to my back. It's super itchy and uncomfortable. :( Why is this happening? and will it ever go away??