If you are sniffling, feeling achy and tired and have a fever, you may be coming down with the common cold or the flu. You are most contagious during the first 24 hours through the first few days of catching a cold virus, and you will feel miserable. With a cold, you will not get much work done, and you'll get well faster if you get some rest. Don't be generous with your germs. Keep your cold to yourself, and stay home!
If you are sniffling but not achy or feverish and feel fine otherwise, you probably have allergies. With allergies, you can go to work. You might want to see an allergist to find out what's triggering your allergies.
How bad is your sore throat?