Suggest Treatment For A Rash On The Upper Abdomen

I recently cut my sugar intake and stopped using artificial sweeteners about a week ago. Two days ago, I started taking a new Multivitamin. Since both, I have developed a rash that began on my upper abdomen. It has spread up and down the front of my trunk and onto my let back. They are small, raised, and Itchy bumps. I can see a lot of red, but it doesn t look nearly as bad in a mirror (less redness from far away). One thing I noticed is I did have a small serving of sorbet today. Around that time, I didn t feel as Itchy as previous or hours since.