 [ Symptoms ] how can an antihistamine cause hives  when i take zertech i break out in hives from head to toe [ Disease ] most helpful answer viruses only last a week but it is possible to get back to back viral infections that seem to last longer one virus mononucleosis can cause a very prolonged sore throat fatigue and white spots on the throat so if this is a possibility your medical provider should order a mono test ebv panel another possibility could be sinusitis where the constant drainage is causing you to have a sore throat it is really up to you how you utilize your financial resources but the only way that you can be properly diagnosed is to be seen by a medical professional that can examine you and order a few diagnostic tests