Why is it that cold sores crop up the night before your 20th high school reunion or that trip to Paris? Fortunately, with a little know-how and the right medication, unsightly sores no longer need to cause a social crisis. Afflicting an estimated 40 million Americans, cold sores result from a herpes simplex virus that lies dormant inside a nerve in the upper jaw. Stress, sunlight, extreme temperatures, and other infections (including colds) can kick the virus into action.

     The key to stopping the sore is to inhibit the reproduction of the virus. Oral prescription medicines, such as Zovirax and Valtrex, work the fastest to accomplish this goal, says Roy S. Rogers III, professor of dermatology at the Mayo Medical Center. A topical solution, Denavir, works the same way and is an option for those who can't take an oral antibiotic or want to improve the sore's appearance immediately.  

     Chronic sufferers should invest in a prescription, but if your flare-ups are rare, try a less potent over-the-counter fix. Pure Lip Remedy uses zinc to slow down viral reproduction and ease the pain. The remedy comes in a daily maintenance formula to ward off outbreaks and a healing version for flare-ups. A little prevention -- wearing an SPF lip balm when you're outside, treating other infections immediately and lowering your stress level -- goes a long way