Cold Sores FAQ

What are cold sores?

Cold sores, also known as fever blisters, are small red sores that occur occasionally on or near your lips or in your mouth. They actually have nothing to do with colds or with fevers; they’re caused by a virus called herpes simplex virus type 1 (HSV-1).

How do you get cold sores?

Nearly nine out of 10 Americans are infected with the cold sore virus at some point in their lives. Most of us pick up the virus through sharing food with or kissing someone who has a cold sore. However, you can also get infected from someone who doesn’t have a visible sore, because some infected people have the virus in their saliva even when they don’t have cold sores. Once you get the virus, it stays in your body for good, hiding in nerve cells near your ear.

HSV-1 is closely related to HSV-2, the virus that causes genital herpes, a sexually transmitted disease. If you receive oral sex from someone with a cold sore, the HSV-1 virus can sometimes cause genital sores. Also, if you give oral sex to someone with genital herpes, the HSV-2 virus can occasionally cause sores in your mouth, which look like cold sores.

What are the symptoms?

When you first catch the cold sore virus, you may have mild flu-like symptoms, including swollen gums, a sore feeling in the mouth, swollen lymph glands in the neck, and fever. You don’t develop cold sores when you’re first infected, and only about a third of all people who catch the cold sore virus will ever develop sores.

If you do develop sores, about a day before you can see any blisters, your mouth will likely tingle, itch, or feel warm in places. Then you’ll see a cluster of small blisters that will turn into a shallow, painful sore. In a few days the sore will crust over and slowly disappear. The whole flare-up lasts about seven to 10 days.

How are cold sores different from canker sores?

Canker sores are red-ringed white sores that can look similar to cold sores but, unlike cold sores, aren’t contagious. Experts aren’t sure what causes canker sores. Commonly cited culprits include stress, vitamin and mineral deficiencies, injury (like scraping your mouth with your toothbrush or a sharp tortilla chip), and astringent chemicals in foods such as lemons or nuts. They usually disappear within 10 days.

What’s the best way to treat cold sores?

Cold sores aren’t very serious for most people, just a little annoying. They go away on their own in one to two weeks, but there are some things you can do to feel better while you have them:

  • Apply ice to cold sores to ease the pain or take a mild pain reliever, such as aspirin or acetaminophen.
  • Avoid salty, spicy, and sour foods, because they aggravate the raw nerves in the sores.
  • Dab on a water-based zinc ointment. It helps dry out the sores so they can heal faster, and may also boost the immune system.
  • Try lemon balm. German studies show that this fragrant herb helps heal sores faster and with less scabbing, especially if it’s applied early in an outbreak. Make a tea of dried lemon balm leaves and apply it to sores with a cotton ball.
  • Take echinacea. Lab research on a topical preparation called ViraMedx (viracea) shows that this herbal remedy can be effective against herpes viruses, even strains that are resistant to the antiviral drug acyclovir. Take echinacea in capsule or tincture form at the first sign of an outbreak, or dab on a topical formula.
  • You may want to try a prescription or non-prescription topical cream or ointment. In some studies, they have been shown to speed up the healing time by a few hours or up to two days. Prescription creams like penciclovir (Denavir) and acyclovir (Zovirax) — and some non-prescription medications like docosanol (Abreva) and tetracaine cream — have been shown to help speed up healing time of cold sores by anywhere from a few hours to two days. (Use these creams only as directed by your physician.)
  • One last caution: When you have cold sores, avoid touching your eyes, because HSV-1 can cause ocular herpes, a serious eye infection.

How can I prevent cold sores?

  • The best thing you can do is keep your immune system as healthy as possible, since outbreaks are most likely to occur when you’re run down. Eat a healthful diet, get enough sleep, exercise regularly, and manage your stress with meditation or other methods.
  • If you have a weak immune system, talk to your doctor about antiviral drugs. The same ones used to lessen an attack can help prevent recurrences.
  • Stay out of the sun, because ultraviolet rays can depress the immune system and trigger cold sores. When you have to be outside, use sunscreen and sunblock-containing lip moisturizers.
  • Eat foods high in the amino acid lysine, such as eggs, potatoes, and dairy products, and avoid foods high in another amino acid, arginine, such as peanuts, rice, and chocolate. The herpes virus needs arginine to replicate, and lysine prevents arginine from getting into your bloodstream. Lysine is also sold as a supplement in health food stores.


American Academy of Dermatology. Herpes Simplex pamphlet.

Thompson KD. Antiviral activity of viracea against acyclovir susceptible and acyclovir resistant strains of herpes simplex virus. Antiviral Res 1998 Jul;39(1):55-61.

Lin L, et al. Topical application of penciclovir cream for the treatment of herpes simplex facialis/labialis: a randomized, double-blind, multicentre, aciclovir-controlled trial. Journal of Dermatological Treatment. 2002 Jun;13(2):67-72.

US Food and Drug Administration. Life Threatening Side Effects with the Use of Skin Products Containing Numbing Ingredients for Cosmetic Procedures. February 2007.

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