Most people with oral herpes do not realize it until they experience cold sores or other symptoms. Some people have just one outbreak and no reoccurrence because the virus stays dormant.
Everything you need to know about cold sores (fever blisters)
Cold sores, or fever blisters, are small, blister-like lesions that form on the lips, chin, cheeks, or in the nostrils, as well as the gums or the roof of the mouth. They result from infection with a herpes simplex virus. Antiviral medications may help manage them.
Cold sores usually cause pain, a burning sensation, or itching before they burst and crust over. People sometimes call them fever blisters.
The most common cause of cold sores is the herpes simplex virus type 1 (HSV-1). Other times, these sores result from an infection with a different strain, called herpes simplex virus type 2 (HSV-2).
In the United States, 48.1% of all people aged 14–49 years have HSV-1, making them more susceptible to cold sores.
There is no way to cure or prevent these sores, but a person can take steps to reduce the frequency and duration of outbreaks.
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The viral strains that cause cold sores, usually HSV-1 and less often HSV-2, are highly contagious and transmit easily during close contact, such as sexual contact.
After the virus enters the body, a person may have:
- flu-like symptoms
- sores in or around their mouth or in their nostrils
- sores around the genital area, in some cases
It is possible for oral herpes sores, or cold sores, to develop around the genitals if transmission happens during oral sex.
A cold sore outbreak typically lasts 1–2 weeks , without treatment, before the body’s immune system suppresses the virus.
The virus does not leave the body, and though it remains inactive most of the time, it can periodically reactivate to cause cold sores.
Most people with oral herpes do not realize it until they experience cold sores or other symptoms. Some people have just one outbreak and no reoccurrence because the virus stays dormant.
Others may have frequent outbreaks that continue for many years.
Some people with oral herpes have no symptoms, and others only experience them after the first exposure to the virus.
Still, at least 25% of people with oral herpes experience reoccurring outbreaks. In this case, cold sores often appear in the same locations each time.
Initial symptoms of an HSV-1 infection may appear 2–20 days after exposure to the virus and can include:
- lesions on the tongue, mouth, chin, cheeks, or in the nostrils
- mouth or tongue pain
- lip swelling
- difficulty swallowing
- a sore throat
- swollen lymph nodes
- a high body temperature
- headaches
- dehydration
- nausea
There may also be an infection of the mouth and gums, known as gingivostomatitis. This lasts for 1–2 weeks and does not reoccur.
Also, in adults, an infection of the throat and tonsils called pharyngotonsillitis may develop with the initial oral herpes infection.
A cold sore develops in several stages when it reoccurs.
- A tingling, itching, or burning sensation around the mouth often indicates the start of an outbreak.
- Painful, fluid-filled sores appear, usually around the mouth.
- The sores break and produce fluid.
- A yellow crust forms on the sores.
- The crust comes off, revealing pink skin that heals in 3–4 days.
Without treatment, most cold sores disappear within 1–2 weeks and do not leave a scar.
People with reoccurring outbreaks can manage them at home by recognizing the signs and using medication.
- Symptoms are severe.
- A cold sore does not start to heal within 10 days.
- The gums swell.
- The person has a weakened immune system.
- Other symptoms are causing concern.
A doctor can usually diagnose the issue by considering the symptoms and making a visual examination, but in some cases — such as if the person has a weakened immune system — they may also order a blood test or take a sample of a sore’s fluid for testing.
Some factors that can weaken the immune system include HIV, medications following an organ transplant, some types of cancer, and some cancer treatment.
Most cold sore outbreaks resolve in 1–2 weeks without treatment.
However, some over-the-counter or prescription medications can shorten an outbreak’s duration and reduce any discomfort or pain, though these do not remove the virus from the body.
In most cases, it is best to use treatments as soon as the first signs of an outbreak appear.
Antiviral creams
Over-the-counter antiviral creams can shorten the duration of an outbreak. Most creams, such as Zovirax and Soothelip, contain acyclovir or penciclovir.
A person should apply the cream to the affected area every 2–3 hours for 5 days.
Oral antiviral medications
Some examples of antiviral medications that a person can take by mouth include:
- valacyclovir (Valtrex)
- acyclovir (Zovirax)
- famciclovir (Famvir)
A doctor may prescribe one of these medications if a person has a weakened immune system or otherwise has regular outbreaks.
A person takes it once or twice a day.
These medications can shorten the duration of an outbreak and may keep them from reoccurring.
Pain relief
Over-the-counter options contain an analgesic such as benzocaine or lidocaine. They do not speed the healing process, but they can reduce discomfort.
Some pain relief medications for cold sores include:
People should dab these ointments, creams, or gels onto the sores with a Q-tip, and it is important not to share these products.
If a person applies the medication with a finger instead, they should wash their hands before and after.
Some alternate options include medications such as ibuprofen (Advil) or acetaminophen (Tylenol).
Home remedies
Some people find that the following home care techniques relieve cold sore symptoms:
- applying cold, soaked tea bags to the area every hour
- dabbing the area with diluted geranium, lavender, or tea tree oil
- using petroleum jelly to keep the skin moist, preventing cracking
There is no scientific evidence that these remedies work or are safe.
Rarely, oral herpes can lead to complications, especially in people with weakened immune systems.
Possible complications include:
- dehydration, if pain from the sores makes drinking difficult
- herpetic whitlow, a painful infection that can occur through a cut on the skin and cause blisters, usually on the fingers
- herpetic keratoconjunctivitis, a secondary infection that can cause eye swelling and irritation, sores on the eyelids, and, without treatment, vision loss
- encephalitis, or swelling of the brain, which may occur if the infection spreads
Encephalitis can be life threatening.
When sores are present, try to:
- Avoid kissing and other skin-to-skin contact involving the affected area.
- Use a dental dam or condom during oral sex.
- Avoid sharing personal items, such as towels and lip balm.
- Follow correct handwashing techniques.
- Avoid touching areas where sores can develop, such as the eyes, mouth, nose, and genitals.
- If touching the sores is necessary, wash the hands with soap and warm water before and after.
Cold sores can be a painful and disruptive symptom of oral herpes.
Many people do not experience complications and can manage outbreaks at home with over-the-counter or prescription treatment.
Anyone with a weakened immune system should let a doctor know if they have cold sores or any other oral herpes symptoms.
Recognizing the early indications of an outbreak and using treatment right away can help. Without treatment, cold sores often disappear within 1–2 weeks .
Last medically reviewed on September 24, 2020
- Dermatology
- Infectious Diseases / Bacteria / Viruses
- Sexual Health / STDs
How we reviewed this article:
Medical News Today has strict sourcing guidelines and draws only from peer-reviewed studies, academic research institutions, and medical journals and associations. We avoid using tertiary references. We link primary sources — including studies, scientific references, and statistics — within each article and also list them in the resources section at the bottom of our articles. You can learn more about how we ensure our content is accurate and current by reading our editorial policy.
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https://www.nhs.uk/conditions/cold-sores/ - Cold sores: Overview. (2018).
https://www.ncbi.nlm.nih.gov/books/NBK525782/ - Cold sores — questions and answers. (2020).
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https://rarediseases.org/rare-diseases/encephalitis-herpes-simplex/ - Herpes simplex virus. (2020).
https://www.who.int/en/news-room/fact-sheets/detail/herpes-simplex-virus - Herpes simplex: Overview. (n.d.).
https://www.aad.org/public/diseases/a-z/herpes-simplex-overview - McQuillan, G., et al. (2018). Prevalence of herpes simplex virus type 1 and type 2 in persons aged 14–49: United States, 2015–2016.
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https://www.ashasexualhealth.org/oral-herpes/ - Porter, D. (2020). What is herpetic keratitis?
https://www.aao.org/eye-health/diseases/herpes-keratitis - Usatine, R., & Tinitigan, R. (2010) Nongenital herpes simplex virus.
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Cold Sores
A cold sore is a group of tiny, painful blisters caused by the herpes simplex virus (HSV). They’re also called fever blisters or herpes simplex labialis.
Up to 90% of people around the world have at least one form of HSV.
The symptoms are usually the most severe the first you time you get cold sores. A first-time cold sore can make a child seriously ill.
After the first outbreak, your body should make antibodies, and you may never have another infection. But many people get cold sores that come back.
Cold Sore Symptoms
Cold sores are most likely to show up on the outside of your mouth and lips, but you can also get them on your nose and cheeks.
You may get cold sores as late as 20 days after you’re infected. The sore might appear near where the virus entered your body.
Cold sores happen in stages:
- You have a tingling, burning, or itching feeling.
- About 12 to 24 hours later, blisters form. The area becomes red, swollen, and painful.
- The blisters break open, and fluid comes out. This usually lasts 2 or 3 days.
- A scab forms on the sore. It might crack or bleed.
- The scab falls off.
You might also have red or swollen gums, swollen glands in your neck, fever, or muscle aches.
First-time infections can also cause:
- Burning and pain inside your mouth
- Sore throat
- Pain when swallowing
- Headache
- Upset stomach
Cold Sore Causes
You catch HSV when you come into contact with people or things that carry the virus. For instance, you can get it from kissing someone who has the virus or from sharing eating utensils, towels, or razors.
Two types of the virus can cause cold sores: HSV-1 and HSV-2. Both types can also cause sores on your genitals and can be spread by oral sex.
Type 1 usually causes cold sores, and type 2 mostly causes genital herpes, but either can be found in both areas.
Certain things can trigger an outbreak, including:
- Some foods
- Stress
- Fever
- Colds
- Allergies
- Fatigue
- Sunburn or being in strong sunlight
- Dental work or cosmetic surgery
- Menstruation
Cold Sore Risk Factors
Cold sores generally aren’t serious, but the infection may be life-threatening for someone who has a weakened immune system because of AIDS, another condition, or medications.
If you have a severe case of a skin condition called eczema, you may get cold sores over large parts of your body.
Cold Sore Diagnosis
Your doctor might diagnose a cold sore just by looking at the blisters. They can also swab the blister and test the fluid for HSV.
Cold Sore Treatment
There’s no cure for cold sores. Once you have the virus, it stays in your body. The sores themselves usually heal on their own in 1 or 2 weeks.
Antiviral medications can speed healing, especially if you take them at the first sign of an outbreak. Your doctor might tell you to use:
- Cream that you apply on the sores. Acyclovir (Zovirax) and penciclovir (Denavir) need a prescription, or you can get docosanol (Abreva) over the counter.
- Pills that you swallow, like acyclovir (Sitavig, Zovirax), famciclovir (Famvir), or valacyclovir (Valtrex). You need a prescription to get these.
- Medicine injected into your bloodstream (called intravenous or IV) if you have a severe case, such as cidofovir (Vistide) or foscarnet (Foscavir). Acyclovir can also been injected.
Some home remedies can help you feel better while you heal:
- Cold, damp compresses
- Pain medicines like acetaminophen and ibuprofen
- Cream painkillers with benzocaine or lidocaine
- Treatments with alcohol to dry out the blisters
- Lip balms and creams to keep moisture in
Cold Sore Complications
Complications from a cold sore are rare, but can happen if the virus spreads to another part of your body, including your:
- Fingers. This infection is called herpes whitlow.
- Genitals. You might have warts or ulcers on your genitals or anus.
- Other areas of skin. If you have eczema and get a cold sore, see your doctor right away to avoid a serious condition called eczema herpeticum. This painful rash covers large areas of skin.
- Eyes. HSV keratitis, an infection in your cornea, can cause blindness.
- Brain or spinal cord. The virus can cause dangerous inflammation called meningitis or encephalitis, especially in people who have weakened immune systems.
Cold Sore Prevention
To lower your risk of another outbreak:
- Get plenty of rest. A lack of sleep weakens your immune system, so you get sick more easily.
- Wear lip balm with sunscreen. Look for SPF on the label.
- Talk with your doctor. If you get sores often, they might have you take an antiviral medicine every day.
To keep from spreading the virus, when you have cold sores, don’t:
- Kiss anyone
- Share eating utensils, glasses, towels, lipstick or lip balm, or razors
- Have oral sex
Keep in mind that you can spread the virus even without symptoms.
Show Sources
Columbia University College of Dental Medicine: “Cold Sores and Fever Blisters.”
Academy of General Dentistry: “What Are Cold Sores?”
MedlinePlus: “Herpes – oral.”
American Academy of Dermatology: “Cold Sores.”
Cleveland Clinic: “Cold Sores.”
Nemours/TeensHealth: “Cold Sores (HSV-1).”
National Library of Medicine: “Zovirax.”
Mayo Clinic: “Penciclovir (Topical Route),” “Acyclovir (Oral Route, Intravenous Route),” “Famciclovir (Oral Route),” “Valacyclovir (Oral Route),” “Cold Sore.”
British Association of Dermatologists: “Eczema Herpeticum.”
Arvin, A., Campadelli-Fiume, G., Mocarski, E., et al., editors. Human Herpesviruses: Biology, Therapy, and Immunoprophylaxis, Cambridge University Press, 2007.
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