Cold sores — also called fever blisters — are a common viral infection. They are tiny, fluid-filled blisters on and around your lips. These blisters are often grouped together in patches. After the blisters break, a scab forms that can last several days. Cold sores usually heal in two to three weeks without leaving a scar.
The small blisters around the mouth and nostrils that define cold sores (also known as fever blisters) are due to a virus that, once contracted, stays with you, hiding until triggered. Anyone can get a cold sore, and most people contract the herpes simplex virus (HSV) through physical contact with an affected person.
Cold sores are small, blister-like lesions that tend to form on the lips, chin, or cheeks, or in the nostrils. They less frequently appear on the gums or the roof of the mouth.
Cold sores spread from person to person by close contact, such as kissing. They’re usually caused by herpes simplex virus type 1 (HSV-1), and less commonly herpes simplex virus type 2 (HSV-2). Both of these viruses can affect your mouth or genitals and can be spread by oral sex. Cold sores are contagious even if you don’t see the sores.
There’s no cure for cold sores, but the good news is that many cold sores usually go away on their own in a week or two and don’t leave a trace.
What Are Cold Sores?
Cold sores are small blisters around the mouth, caused by the herpes simplex virus. They are sometimes called fever blisters. The most common strain of the virus causing cold sores is herpes simplex virus. It can be spread by kissing or sharing eating utensils or even sharing towels.
Herpes simplex is not curable, but may lie dormant for a long time. Episodes of the cold sores last no longer than 2 weeks. Hot sun, cold wind, a cold or other illness, or a weak immune system can cause an outbreak of herpes simplex virus.
Signs and Symptoms of Cold Sores
Symptoms of cold sores vary, with the first exposure or primary outbreak usually being the most severe, says Allison Arthur, MD, a board-certified dermatologist based in Orlando, Florida.
According to the American Academy of Dermatology, first-time cold sore symptoms may include:
- Painful blisters on the lips, cheeks, mouth, nose, or throat (which eventually pop and form scabs)
- Mouth and throat pain
- Swelling in the neck
- Fever and body aches
You’ll still have painful blisters with recurrent outbreaks, but the more severe symptoms, like body aches and a fever, are less likely to return.
It’s important to note that while cold sores typically form outside of the mouth, these sores can form inside the mouth during your first outbreak. This is known as acute herpetic gingivostomatitis. For this reason, you might initially mistake a first-time cold sore for a canker sore. Canker sores are ulcers that form on the mucous membranes inside the mouth or on the tongue, per the Mayo Clinic
A cold sore can develop anytime after you’re first infected with a herpes simplex virus (HSV). You may also notice early signs of an outbreak one or two days before a blister appears.
Early symptoms of a cold sore may include:
The blister appears within 24 to 48 hours of the first symptom. After a couple of days, the blister will burst and ooze with pus. A scab will then form over the blister.
After initial symptoms develop, it can take two to four weeks to heal completely. During that time, cold sores go through three distinct stages. The symptoms and stages of an outbreak can vary depending on whether or not this is your first case or a recurrence.
During the first stage of a cold sore outbreak—or the first one to two days, approximately—many people experience tingling, itching, or even soreness around the mouth.2
If you’re having a recurrence, you’ll likely feel these sensations in the same locations as previous outbreaks. Some people experience these sensations and never actually develop fluid-filled blisters.
After a few days, small, hard, fluid-filled blisters begin to form on the lips, nose, cheeks, or other parts of the face.2 If you develop a blister (or blisters) near the eyes, make an appointment with an eye doctor immediately. Watch out for eye symptoms, such as sensitivity to light, pain, or grittiness in the eyes.
At this stage, the blisters and fluid are extremely contagious, so it’s important to avoid close physical contact with others. You can also spread blisters to other locations on the body by touching sores and then another body part. If you touch a cold sore, wash your hands immediately.
The blisters may merge together and burst, resulting in small, open sores that ooze fluid.2 These sores are very painful and highly contagious. After a few days, the open sores will begin to dry out and scab. Scabs can be very itchy and even crack, so avoid biting or picking at them, as this can worsen discomfort.
Between five and 15 days after the initial outbreak, scabs will begin to fall off and affected areas will begin to heal.
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 happensTrusted Source during oral sex.
A cold sore outbreak typically lasts 1–2 weeksTrusted Source, 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 frequentTrusted Source outbreaks that continue for many years.
People with reoccurring outbreaks can manage them at home by recognizing the signs and using medication.
However, consult a healthcare provider if:
- 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.
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).
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
It’s not possible to prevent infection with the herpes simplex virus or prevent outbreaks of cold sores, but you can take steps to minimise the spread of infection.
Cold sores are at their most contagious when they burst (rupture), but remain contagious until they’re completely healed. Avoid close contact with others until your cold sore has completely healed and disappeared.
However, there’s no need to stay away from work or miss school if you or your child have a cold sore.
You can help minimise the risk of the cold sore virus spreading and cold sores recurring by following the advice below:
- avoid touching cold sores unless you’re applying cold sore cream – creams should be dabbed on gently rather than rubbed in, as this can damage your skin further
- always wash your hands before and after applying cold sore cream and after touching the affected area
- don’t share cold sore creams or medication with other people as this can cause the infection to spread
- don’t share items that come into contact with the affected area, such as lipsticks or cutlery
- avoid kissing and oral sex until your cold sores have completely healed
- be particularly careful around newborn babies, pregnant women and people with a low immune system, such as those with HIV or those having chemotherapy
- if you know what usually triggers your cold sores, try to avoid the triggers – for example, a sun block lip balm (SPF 15 or higher) may help prevent cold sores triggered by bright sunlight