Are Cold Sores and Fever Blisters Caused by Colds?

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Cold sores—also known as fever blisters—are not caused by the common cold but they are related. They are caused by a different type of virus known as herpes.

Typically, cold sores on the mouth are caused by herpes simplex 1 (HSV-1), while herpes simplex 2 (HSV-2) causes sores in the genital area. However, it is possible for either virus to cause sores in either area.

Woman applying cold sore cream on lips in front of mirror
belchonock / Getty Images


Nearly everyone has the HSV-1 virus inside their body by the time they reach 10 years old. Not everyone will experience symptoms though.

If you are infected with HSV-1, the first time it makes you sick can be very different from the cold sores you experience after that. During first time infections, people may experience:

  • Fever
  • Sore throats
  • Headaches
  • Muscle aches
  • Swollen lymph nodes

After the first infection, you may experience tingling or itching around the area a day or two before a cold sore appears. Then, the small blisters that are filled with fluid form somewhere around the edge of your lips. They may also appear around the nose or cheeks.

The blister will then burst and ooze fluid until they crust over after a few days. The scabbed area should disappear within two weeks.

If you carry HSV-1, you may experience cold sore "breakouts" throughout your life. They can be triggered by stress or illness, which may be why they got the name cold sores and fever blisters. Although they can develop during an illness such as a cold or the flu, cold sores are not actually caused by the cold or flu viruses.


Most cold sores do not require treatment. They will go away on their own within two weeks. If they do not, they occur very frequently or they appear in multiple places on the body, you should contact your healthcare provider.

There are over-the-counter (OTC) treatments that may help with your symptoms. These include Abreva (docosanol), OTC remedies that contain a drying agent, and ice or cold compresses to relieve pain.

If your healthcare provider decides that your symptoms are severe enough that you need prescription treatment, there are several antiviral medications they may prescribe. These include:

  • Acyclovir
  • Valacyclovir
  • Famciclovir
  • Penciclovir

These may be available as a cream or pill, although the pills are generally more effective. If the infection is widespread and severe, it may require IV treatment and hospitalization.

Alternative therapies may be used to try to treat cold sores as well. Although the efficacy of these treatments is unclear, there is some evidence that lemon balm (lip balm containing 1% lemon extract) may help shorten healing time and prevent a recurrence. Lysine has also been used as a supplement to help with cold sores.

When to Be Concerned

If your cold sore does not go away within two weeks, you should contact your healthcare provider. People with weakened immune systems are at higher risk for complications from cold sores than others.

Other things to watch for and seek medical treatment for include:

  • Infection or blisters on the eye
  • Cold sores all over the body (this can occur in people who also have eczema)


If your outbreaks are triggered by stress, using stress-reducing techniques such as deep breathing or meditation may help. You should avoid contact with others while blisters are present—especially kissing and sharing food or eating utensils.

Be careful about touching other parts of your body when blisters are present as the virus can spread. This can be very dangerous, especially if it gets into the eyes.

Wash your hands frequently. If you have a cold sore, be sure to wash your hands frequently to avoid spreading the virus to other people.

If you get cold sores a lot, talk to your healthcare provider to see if taking an antiviral medication on a regular basis may help you.

Frequently Asked Questions

  • What is the difference between a cold sore and a fever blister?

    Cold sore and fever blister are two different terms for the same ailment: a herpes simplex virus 1 blister on or around the lips. The virus attacks the cells around the mouth, causing a red and inflamed sore.

  • Does stress cause fever blisters?

    Yes and no. Fever blisters are caused by the herpes simplex virus 1 (HSV-1). Once you contract the virus it stays in your system and can lay dormant for years. Physical or emotional stress can trigger the virus to reactivate causing a breakout. In addition, when we are under stress we often don't get enough sleep, exercise, or proper nutrition. This can contribute to a fever blister outbreak.

  • How can you tell the difference between a cold sore and a pimple near the mouth?

    A pimple near the mouth can be confused with a cold sore, but there are a few differences. If it is on your lip, it is a cold sore. You cannot get a pimple on your lip. A pimple forms a red bump, but not a blister. A cold sore is a cluster of tiny blisters. Pimples can hurt, whereas cold sores tingle and burn. A pimple will clear up after a few days, but a cold sore will crust over. 

3 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Chi CC, Wang SH, Delamere FM, Wojnarowska F, Peters MC, Kanjirath PP. Interventions for prevention of herpes simplex labialis (cold sores on the lips). Cochrane Database Syst Rev. 2015;(8):CD010095. doi:10.1002/14651858.CD010095.pub2

  2. Mailoo VJ, Rampes S. Lysine for herpes simplex prophylaxis: A review of the evidence. Integr Med (Encinitas). 2017;16(3):42-46.

  3. Cunningham A, Griffiths P, Leone P, et al. Current management and recommendations for access to antiviral therapy of herpes labialis. J Clin Virol. 2012;53(1):6-11. doi:10.1016/j.jcv.2011.08.003

Additional Reading
  • Cold Sores. MedlinePlus 18 Sep 13. US National Library of Medicine. Department of Health and Human Services. 24 Oct 13.
  • Cold Sore. Diseases and Conditions 23 May 13. Mayo Foundation for Medical Education and Research. 24 Oct 13.

By Kristina Duda, RN
Kristina Duda, BSN, RN, CPN, has been working in healthcare since 2002. She specializes in pediatrics and disease and infection prevention.