The herpes simplex virus (HSV) causes cold sores, also known as fever blisters. These sores are highly contagious.
If you have an oral HSV infection and kiss someone, the other person may catch the virus. Rarely, you can spread it through aerosol transmission. HSV can survive for short periods outside the body, meaning it’s possible to transmit HSV and cold sores through contaminated surfaces and objects.
While cold sores typically clear up within 7–15 days, sometimes they can last longer. The more time that goes by without treatment, the longer the cold sore will take to heal.
Treatment options include over-the-counter medications like Abreva or prescription treatments like Valtrex. While these treatments do not cure the infection, they reduce healing time and decrease the likelihood of the virus spreading to other people.
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The highly contagious herpes simplex virus causes cold sores. This virus has two types:
HSV-1: Usually causes cold sores on the mouth
HSV-2: Usually causes sores on the genitals
Once you have the virus, it stays in your body for life. It can reactivate spontaneously, and scientists believe multiple flare-up triggers exist, including:
Being ill with an infection or fever
An injury to the affected area
A cold sore can last up to 15 days, but many things can cause complications and lead to healing taking longer than expected.
For example, the healing process may take longer than usual if you have another type of infection or an allergic reaction. If you take medication that suppresses your immune system, this can also affect healing time.
It's important to know what complications may arise when managing treatment for cold sores so you can respond accordingly to ensure quick, complete healing.
After initial HSV exposure, most people experience their first cold sore outbreak within 2–12 days. While HSV-1 typically causes oral lesions, symptoms vary with age.
A child may experience herpetic gingivostomatitis, which is a very painful condition causing blisters on the lips and canker sores (ulcers) in the mouth. On the other hand, an adult may have a sore throat (herpetic pharyngitis) on infection with the herpes virus. This is most common in young adults.
If you have recurrent cold sores, the first indication of a flare-up is usually tingling, itching, or pain around your mouth. Small red bumps form on your lips before breaking open to form painful ulcers.
While the herpes simplex virus causes cold sores, people confuse them with other conditions:
Inflammation of the corners of the mouth, causing them to swell and crack
They may need treatment with antibiotics or antifungal medication
Easily mistaken for cold sores because of their appearance and symptoms
Only symptomatic treatment is available
A common condition that mimics a cold sore
Healing may take longer than expected because of irritation around the mouth
Frequent application of lip balm or petroleum jelly can relieve symptoms
Cold sores are a virus symptom, while angular cheilitis is inflammation with several possible causes.
People may confuse these two conditions because they share symptoms, but they are different. Angular cheilitis causes dryness and painful cracks at the corners of your mouth, usually due to a bacterial or fungal infection. Cold sores typically look like blisters that break open and ooze.
Cold sores can lead to complications. A complication is a secondary disease or condition aggravating an already existing one.
In the case of cold sores, complications can stem from:
Picking at or popping the cold sore
Scratching the wound
If you have a secondary infection, the healing process will take longer. Contact your physician for the best treatment plan.
Doctors typically don’t recommend topical ointments, such as acyclovir or valacyclovir cream, as they offer minimal benefits. Your doctor will prescribe oral antivirals as appropriate.
Healing may take longer than expected for many reasons, and these complications sometimes require medical attention.
Indications that your body is struggling to fight off the virus include:
Cold sores come in quick succession, and you continue to have outbreaks for months
An individual outbreak doesn’t improve after two to three weeks
If this happens to you, see a doctor. They can advise the best course of action.
If you think you may be developing a cold sore, wash your hands frequently to avoid spreading the virus to other body parts.
You should also avoid close contact with other people until all blisters have completely healed because there is a risk they could catch the virus. Children and pregnant women are particularly at risk from HSV complications.
Preventing cold sores involves avoiding triggers if you already have the virus. If you don’t have the virus, practice safe sex and avoid kissing people with cold sores. However, HSV is still transmissible even without obvious sores, so it’s impossible to prevent it completely unless you abstain from touching other people entirely.
Although there is no cure for HSV-1, people use many methods to shorten the duration of an outbreak or increase the time between recurrence. Some are doctor-recommended, and others are common in old wives’ tales.
Over-the-counter medicines don’t require a doctor's approval and are readily available at the first sign of a flare-up. Some of the most common medications are:
Abreva cold sore cream
Zilactin cold sore gel
Compeed cold sore patches
Prescription antiviral medications to combat cold sores include acyclovir, valacyclovir, and famciclovir. The use of antiviral therapy blocks the replication of the virus, shortening the length of symptoms and decreasing the risk of spreading the virus.
While they don’t have as much science backing up their efficacy, some people claim that home remedies such as lemon balm, aloe vera, and garlic can soothe the discomfort associated with cold sores.
Be cautious when using home remedies, as some may cause a painful reaction or worsen your symptoms. It’s often best to ask your doctor or pharmacist for their recommendations.
See a doctor if your cold sore takes longer than expected to heal. They may prescribe an antiviral medication.
Cold sores usually take around two weeks to heal. However, sometimes they can last much longer due to complications, such as a secondary infection.
If you have a stubborn cold sore that won’t go away, consult your doctor. They will advise you on the best steps and may prescribe you a cream or antiviral medicine.
Herpes simplex virus (HSV) infections | Merck Manual
Viral pharyngitis (2017)
Cold sores: Diagnosis and treatment | American Academy of Dermatology Association