What Causes Breathing Difficulty And Runny Nose?

My mother is having difficulty breathing through her nose. She is 94 years old and recently had shingles, from which she is now recovered but still has pain from that sometimes. I am alarmed because at night it is hard for her to sleep since she has had a runny nose and the breathing problems for over a week now. We thought it was a cold, but she does not seem to have any other cold symptoms (sore throat, etc.)