I have been suffering from acid reflux and being sick and recently came out in a blood red rash which did go down what could it be?
Can't tell here. Can't tell what that is in this forum. Some conditions can cause rash/flushing and excess acid production, but can't tell without exam. See your doc.
Possibly petechiae. You didn't say if you were vomiting or where the red rash was located, but with frequent or vigorous vomiting, tiny red spots called petechiae can develop. These are tiny bleeding spots in the skin, often on the face or neck. They will resolve without treatment and are not dangerous.