I have a painful swelling under my eye, with redness near the tear duct. much worse today then it was yesterday. don't remember being bitten.

Cellulitis Vs. Stye: This sure sounds like an urgent problem requiring medical intervention and probably treatment. Please get to your doctor's office urgently today.

Stye: This is probably a stye, but may be a blocked tear drain near the nose. Try hot compresses 3 times daily for at least 5-10 minutes. See an eye doctor if the swelling increases, if you develop a fever, or if it isn't getting better in a few days.