Cold sores are fluid-filled blisters on or around the lips caused by the herpes simplex virus (HSV), which is contagious until the cold sore is fully healed.
Cold sores, commonly referred to as oral herpes or fever blisters, are contagious because HSV spreads through close contact from person to person (for example, kissing). Once infected, the virus lives dormant in the nerves in the skin for the rest of your life and can come back at random.
“Oral herpes is contagious even if you can’t see the sores yet,” said Dr. Maggie Moses, dermatologist at Marshfield Clinic Health System. “However, they are much more contagious when the sore is present. Cold sores are contagious until the blisters crust over and heal completely.”
More than 50% of adults in the U.S. have the virus that may cause cold sores, which makes it very common.
“Cold sores and genital herpes are actually closely linked as they are both infections that result in blisters caused by the herpes simplex virus,” said Dr. Moses. “However, genital herpes is typically caused by herpes simplex virus type 2 and seen in the genital area, while cold sores on the lips is classically caused by herpes simplex virus type 1. However, we are seeing both types of viruses in either locations more frequently.”
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Cold sore stages
Cold sores typically take 5-10 days to heal, going through these five primary stages during that time:
- Tingling: This is the stage where you first feel a tingling sensation underneath the skin. You may not even see the cold sore at this point. Some people feel itching or burning sensations as well. The cold sore is contagious in this stage.
- Blistering: This is the stage where the cold sore starts to form fluid-filled blisters on or around the lips. The cold sore is contagious in this stage.
- Weeping: In this stage, the blisters pop and the fluid comes out of the blister. The cold sore is contagious in this stage.
- Scabbing: The cold sore will eventually scab over or crust, and no more fluid will come out. The cold sore is still contagious in this stage.
- Healing: The scab goes away and the cold sore is fully healed. The cold sore is no longer contagious in this stage.
Treating cold sores
You can begin to treat cold sores as soon as you feel the tingling sensation. Most doctors recommend using antiviral medications available over-the-counter, such as Abreva, or by prescription, such as valacyclovir and acyclovir. These medications reduce symptoms, lessen pain and help speed healing.
“Some people use antivirals regularly to suppress cold sores from developing,” Dr. Moses said. “Also, applying a cold washcloth to the sore may help soothe symptoms and reduce inflammation.”
Fever blisters most typically appear on the outside of the lips and mouth, but can form on the nose or face.
Oral herpes can be triggered by:
- Sickness
- Stress
- Hormonal changes
- Compromised immune system
- Sun exposure
- Heavy winds
Because the virus lives dormant inside you, there is no cure for oral herpes once you have your first outbreak. There is no way to prevent fever blisters other than trying to avoid triggers as much as possible.
Preventing herpes simplex virus
The best way to prevent cold sores is to reduce skin-to-skin contact with someone that has a cold sore, which is when they are most likely to spread HSV.
If someone has an active cold sore, do not share lip balm, a drinking glass, silverware, utensils, towels or pillows with that individual.
“If you have a sore or feel one coming, don’t kiss babies,” Dr. Moses said. “The virus can be deadly for newborns and cause encephalitis, fevers and other illnesses.”
For people who have a compromised immune system or HIV, the virus also could be very harmful.
“You can be more susceptible to the herpes virus when you’re ill with the common cold so you could have it when you’re sick,” Dr. Moses said.
For questions about cold sores, talk to a Marshfield Clinic Health System provider.
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