Can Viral Infection Lead To Blisters And Rashes?

I have been told i have a viral infection throughout my body. It started 6 days ago. I have been training for a marathon and after a run on saturday started feeling quite poorly. All my joints and muscles ached severely and then i got a high temp. By sunday i couldnt walk due to swelling on my knees, my back was painful and my neck was very sore. I noticed small blister rash under the skin on my feet. The doctor prescriped Klaricid 500mg and diclofenac. by tuesday, the rash had gone all over my feet, itching, tightening and i had started to get severe ulcers in my mouth and my tongue was selling. I had to go to A & E. Bloods where done and I was told that i certainly had an infection but glandular fever was ruled out. I was sent home to continue the medication along with prednisolone x 40mg per day for 3 days and chlorphenamine. Although my joints are easing off slowly, my tongue is now fully covered in very painful ulcers and the rash has spread to my hands. Could this be an allergic reaction to the meds.?