Are Cold Sores and Fever Blisters Caused by Colds?

cold sore
Are cold sores caused by colds?. Todd Keith/E+/Getty Images

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.

How Cold Sores Start

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 Throat
  • Headache
  • Muscle Aches
  • Swollen Lymph Nodes

What To Expect

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 "break outs" 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.

Treatment Options

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 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 health care 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 percent lemon extract) may help shorten healing time and prevent 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 health care 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 other 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 health care provider to see if taking an antiviral medication on a regular basis may help you.


Cold Sore. Diseases and Conditions 23 May 13. Mayo Foundation for Medical Education and Research. 24 Oct 13.

Cold Sores. MedlinePlus 18 Sep 13. US National Library of Medicine. Department of Health and Human Services. 24 Oct 13.

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