What is a cold sore and how is it treated?

Share this article

Caused by herpes simplex virus (HSV) type 1 or type 2, cold sores are groups of fluid-filled blisters.

Cold sores are unpredictable and highly contagious.¹ The virus is spread through saliva and close contact with others. Sharing drinks, utensils, and lip balm can put you at increased risk for contracting and passing the virus that causes cold sores.

Although cold sores are bothersome and may feel embarrassing, they are quite common. Over 50% of Americans have been infected with the herpes simplex virus type 1, although only 20 to 40% of infected people are symptomatic. Some people with HSV-1 — the type of herpes most often responsible for cold sores — never develop a cold sore.²

A background decorative of Blue color

Cold sore symptoms

If you’ve never had a cold sore in the past and are wondering if you have one now, you may have a million questions about symptoms and next steps. The first time you have a cold sore outbreak after contracting the virus, you may develop a fever and have a feeling of malaise, however symptoms of exposure are generally mild and you might not know exactly when you’ve been exposed.³

Cold sore outbreaks typically include:

  • A tingling, burning, or itching sensation on or around the lips. This sensation usually develops about 12 to 24 hours before the cold sore forms.

  • Redness, swelling, and pain at the area of outbreak.

  • Sores that rupture and ooze clear or slightly yellow fluid.

  • Scabbing that occurs over the sore.

  • Cracking or bleeding on and/or around the sore.

  • Pink or red skin at the outbreak site after the scab falls off.⁴

How are cold sores diagnosed?

Diagnosing cold sores is rather straightforward. A physician can usually diagnose cold sores purely based on the outbreak’s appearance. For formal confirmation, your doctor may swab the cold sore to test the fluid for the presence of herpes simplex virus.⁵

How long do cold sores last?

While the duration of a cold sore outbreak is different for everyone, the average cold sore lasts about one week, but may take up to two weeks to fully heal.⁶ The cold sore starts as a blister and eventually bursts, at which point a scab forms over the sore. The exact length of a cold sore outbreak varies from person to person and there isn’t medicine available that can accelerate healing.

What triggers cold sores?

Cold sores can be triggered by a variety of factors—some of which may seem random or strange—which is part of the reason why outbreaks can seem unpredictable. Some of the most common triggers of cold sores are:

  • Physical stress

  • Emotional stress

  • Fever

  • Illness

  • Fatigue

  • Extreme temperatures (hot, cold, wind)

  • Hormonal changes (menstruation, pregnancy)

  • Sunburn

  • Damaged or cracked lips

Some people with the cold sore virus experience outbreaks seasonally or even monthly, others experience symptoms whenever they’re ill and some people with the virus never have outbreaks. Regardless of the frequency of symptoms, the virus remains dormant in a group of facial nerve cells called the trigeminal ganglion until if and when the virus is triggered next.⁷

Cold sore treatments

If you have a fever blister and want to know what to do for a cold sore, you’ll be happy to know there are options. Treatment for cold sores typically include over-the-counter (OTC) topical anesthetics and protectants, anti-inflammatory agents, or topical antiviral agents. If you apply these medicines at the very onset of symptoms as soon as you notice the tingling sensation you may be able to prevent the cold sore from appearing altogether.⁸

Dentists can prescribe topical or systematic antiviral drugs, however their application is highly situational and dependent on the individual patient.⁹ In the most severe of outbreaks, antiviral medicine may be prescribed intravenously.¹⁰ This is a rare form of cold sore intervention, and for most outbreaks, OTC medicine, rest and time will do the trick.

It’s important to note that the herpes virus cannot be cured; these are just temporary fixes to provide pain relief and less stress during an outbreak.

Cold sore complications

Complications from cold sores are rare, but there are some concerns to be aware of.

HSV keratitis

Since the herpes simplex virus is so contagious, there is a risk for eye infection when touching your eye after touching your cold sore. HSV keratitis is the most severe form of eye infection possible as a result of a cold sore outbreak and in some cases can lead to blindness.¹¹

Genital sores

HSV-1 is the herpes simplex virus typically responsible for cold sores, but it can be spread to the genitals via oral sex — therefore causing genital and anal warts.¹²

Additionally, people in vulnerable populations should be aware of the risks associated with cold sores. If you’re in one of the following categories and have a cold sore, you should seek medical treatment immediately:

  • Babies - Babies who are six months and younger may experience high fever, seizures and other complications as a result of their partially developed immune system.¹³

  • People with eczema - While eczema isn’t particularly serious in general, it can cause complications in people who have cold sores. The herpes simplex virus can cause a fatal infection called eczema herpeticum.¹⁴

  • People who are immunocompromised - People with weakened immune systems are at risk for encephalitis, which is swelling of the brain. Those living with HIV or undergoing chemotherapy may also experience longer and more severe outbreaks than someone who is otherwise healthy.¹⁵

Outside the aforementioned exceptions, mouth sores like cold sores and canker sores are usually harmless. Thus, in most cases there is no need for concern. However, you should schedule an appointment as soon as you noticed any changes within or around your mouth — even if you’re not experiencing any pain. A dentist can assess your sores, potentially take a biopsy¹⁶ and ensure that your health remains a priority.

Links to external sites are provided for your convenience in locating related information and services. Guardian, its subsidiaries, agents and employees expressly disclaim any responsibility for and do not maintain, control, recommend, or endorse third-party sites, organizations, products, or services and make no representation as to the completeness, suitability, or quality thereof.

Brought to you by The Guardian Life Insurance Company of America (Guardian), New York, NY. Material discussed is meant for general illustration and/or informational purposes only and it is not to be construed as tax, legal, investment or medical advice. It is not dental care advice and should not be substituted for regular consultation with your dentist. If you have any concerns about your dental health, please contact your dentist's office. Guardian Direct plans are underwritten and issued by The Guardian Life Insurance Company of America New York, N.Y. or its subsidiaries. Products are not available in all states.


Insights for the people.

Join our new digital insurance community that includes tips, resources and useful information from Guardian Direct.


  1. https://www.mayoclinic.org/diseases-conditions/cold-sore/symptoms-causes/syc-20371017?page=0&citems=10, 2018

  2. https://my.clevelandclinic.org/health/diseases/21136-cold-sores, 2019

  3. https://my.clevelandclinic.org/health/diseases/21136-cold-sores, 2019

  4. https://my.clevelandclinic.org/health/diseases/21136-cold-sores, 2019

  5. https://my.clevelandclinic.org/health/diseases/21136-cold-sores/diagnosis-and-tests, 2019

  6. https://my.clevelandclinic.org/health/diseases/21136-cold-sores, 2019

  7. https://my.clevelandclinic.org/health/diseases/21136-cold-sores, 2019

  8. https://my.clevelandclinic.org/health/diseases/21136-cold-sores/management-and-treatment, 2019

  9. https://my.clevelandclinic.org/health/diseases/21136-cold-sores/management-and-treatment, 2019

  10. https://my.clevelandclinic.org/health/diseases/21136-cold-sores/management-and-treatment, 2019

  11. https://my.clevelandclinic.org/health/diseases/21136-cold-sores/management-and-treatment, 2019

  12. https://my.clevelandclinic.org/health/diseases/21136-cold-sores/management-and-treatment, 2019

  13. https://my.clevelandclinic.org/health/diseases/21136-cold-sores/management-and-treatment, 2019

  14. https://my.clevelandclinic.org/health/diseases/21136-cold-sores/management-and-treatment, 2019

  15. https://my.clevelandclinic.org/health/diseases/21136-cold-sores/management-and-treatment, 2019

  16. https://my.clevelandclinic.org/health/diseases/21136-cold-sores/management-and-treatment, 2019