My left neck lymph swells up with no other problems accompanying it and then goes away and returns weeks or months later. This has been going on for over a year. It was swollen again a few months ago and did accompany a terrible sore throat and fever. I admitted myself to the emergency room and was tested for Mono, Strep, etc. Both tests came back negative. I was given antibiotics (as well as a very strong shot of an antibiotic in case of an STD as a precautionary measure). The swelling went away but has returned again - this time with no other side effects. I don't have a cold or fever or sore throat, etc. I feel fine otherwise. What in the world can this be?