 [ Symptoms ] does exercise boost endorphins in those with fibromyalgia [ Disease ] yes a z pac can cause hives or rashes as i know from first hand experience when i was younger i was prescribed amoxicillin when i had strep throat and an hour or so after taking it i broke out in hives and had to go to the hospital oddly enough i have taken amoxicillin when i was sick prior to this experience with no allergic reaction i recommend trying a different antibiotic since there are plenty out there hope this helps