Cold sores spread through direct contact with someone who has them. Maybe you kissed someone who had an active cold sore, or you could have gotten the virus merely by touching the hand of someone who touched her own cold sore a few minutes before. The first cold sore that you experience is probably the worst. Afterward, the virus lurks in your system forever, lying dormant among the nerve ganglia beneath your skin’s surface, waiting to be reactivated, says Lenore S. Kakita, MD, clinical assistant professor of dermatology at UCLA and an adviser to the American Academy of Dermatology. The good news, says Dr. Kakita, is that most people develop a slight immunity to them over the years, making outbreaks fewer and farther between. In women stress is the biggest trigger for cold sores, but weather changes, especially excessive sunlight, can bring on outbreaks, says Dr. Kakita. When you get stressed, your resistance to disease drops, and that can awaken the dormant herpes virus within your nerve ganglia cells, prompting an outbreak.  Menstruation can also instigate cold sores in some women, but probably more as a result of stressful feelings at that time of the month rather than a direct result of hormone levels, adds Dr. Kakita. MORE: 2-Minute Stress Solutions

Treatment

Left alone, a cold sore will normally last 10 to 14 days, says Dr. Kakita. Aside from taking the prescription drug acyclovir (Zovirax), here’s what else you can do to minimize the discomfort on your own or shorten the duration of an attack: Grab an ice cube. Applying ice directly to the sore can bring the swelling down and provide temporary relief, says Geraldine Morrow, DMD, past president of the American Dental Association and a dentist in Anchorage, Alaska. Protect your lips. If you have had an outbreak of cold sores in the past, you should wear a lip balm with a sun protection factor (SPF) of 30 at all times, but especially when you are outdoors in the sun, says Dr. Kakita. If you have an open cold sore, don’t use the balm stick directly on your lips, or you’ll spread the virus around, says Dr. Kakita. Instead use a cotton swab to apply balm not only to your lips but also to the skin around the outside border. Hands off. People don’t realize how highly contagious cold sores are, says Dr. Morrow. “If you have a cold sore on your lip, don’t touch it. You could get very, very painful cold sores on your hands, especially if the fluids from the blister get under a hangnail,” she says.  Give lysine a try. Dr. Kakita recalls that before the advent of acyclovir, people swore by the preventive and healing properties of lysine, an amino acid that counteracts arginine, a substance in various foods that in some people seems to trigger cold sores. “Some people still take lysine tablets,” she says. Sleep upright. If you have a cold sore, Dr. Kakita recommends propping a few pillows behind your head at bedtime, letting gravity help the blisters drain. Otherwise fluid may settle in your lip during the night.  Reschedule your dental appointment. The last thing that you want to do when you have a cold sore is “open wide,” says Dr. Morrow. The movement will stretch your lips, aggravating your tender cold sore, and it could cause it to break open and spread.

When to See a Doctor

Prescription medications such as acyclovir (Zovirax) are available to fight the herpes simplex I virus responsible for cold sores, and they can stop a cold sore in its tracks, says Dr. Kakita. If you’re bothered by frequent, severe cold sores, it makes sense to see your doctor. Even if a cold sore develops, the outbreak will be milder, less painful, and shorter if you’re taking medication. MORE: 8 Surprising (And Natural) Ways To Beat Pain