Cold Sores

What Is a Cold Sore?

Also known as ulcers, lesions, and fever blisters, cold sores are small blisters that form on or around the lips. They’re usually caused by the herpes simplex virus type 1 (HSV-1), which affects 3.8 billion people under age 50 worldwide, but may also be caused by type-2 herpes virus (HSV-2).

Not to be confused with canker sores, which can be caused by stress or trauma to the mouth, cold sores are spread through saliva or close contact with a person who has HSV-1 or HSV-2. Though you’re more likely to catch oral herpes when a person has an active cold sore, the virus can also spread when someone has no symptoms.

There’s a lot of stigma attached to cold sores, as well as many misconceptions. For example, herpes is typically thought of as a sexually transmitted disease (STD), but the type that causes cold sores is often transmitted in childhood through close skin-to-skin contact. One older study found more than 25 percent of kids are infected by age 7.

In this guide, we’ll set the record straight about cold sores, including what causes them, what increases your risk, and treatments that can help.

What Does a Cold Sore Look Like?

A cold sore appears as a cluster of small, fluid-filled blisters on or around the lips. It may be red, swollen, and painful to the touch, and can become crusted over after a day or two.

There are various cold sore stages during which its appearance changes:

• Prodrome: The first stage occurs about a day or two before cold sores appear. You may feel itching, tingling, or burning at the site where your blister will emerge.

• Blistering: In the next stage, a painful blister or group of blisters will emerge in or around the mouth.

• Oozing: Eventually, these fluid-filled blisters rupture and ooze or weep a yellowish liquid.

• Crusting: When the liquid dries out, your blister becomes crusty, and a scab appears over the cold sore.

• Healing: The scab eventually falls off and fades away. Healing time can last a few weeks, during which you are still contagious.

Are Cold Sores Always Herpes?

Yes, cold sores are always herpes. However, herpes doesn’t always cause cold sores. According to the CDC, most people with HSV-1 don’t get cold sores, but they can still spread the virus to others.

Viral shedding is when the body releases infectious viral particles that are highly contagious. It can happen whether or not symptoms are present. Some research suggests at least 70 percent of the population sheds HSV-1 asymptomatically at least once a month, and some appear to shed HSV-1 more than six times per month

Cold Sore Symptoms

The first time a person has a cold sore, their symptoms tend to be more severe and long-lasting. In addition to the small, fluid-filled blisters that occur on or around the mouth and lips, other symptoms of cold sores that may appear during the first outbreak include:

• Fever

• Body aches

• Pain while swallowing

• Sore throat

• Nausea

• Headache

• Swollen lymph nodes

After you are infected with the virus that causes cold sores, it will remain in your nerve cells until it’s reactivated. However, not everyone with HSV has recurrent outbreaks. If you do have another outbreak, you’ll likely experience itching, tingling, and burning before a lesion appears. Symptoms of repeat outbreaks tend to be less severe.

If you get a cold sore on your lips, you’ll notice that only one side of your face is affected. You can also get a cold sore inside the mouth or on other parts of the face, including the nose and cheeks.

How Long Does a Cold Sore Last?

Cold sore outbreaks typically last about one to two weeks. You may be able to speed up this process by taking antiviral medicines like valacyclovir (Valtrex®). We’ll go into more detail about how antivirals work later.

After the cold sore goes away, you typically won’t see any visible scars from the sores.

What Causes Cold Sores?

You already know cold sores are caused by herpes simplex virus type 1 or type 2. And you know HSV viruses are typically spread through saliva and direct contact with someone who has sores or who is shedding the virus without symptoms. While kissing is the most obvious way to get HSV-1, it isn’t the only way. You can also get it by sharing utensils, drinkware, razors, towels, lip balm, and other items with someone who has the virus.

HSV-1 and HSV-2 infections can also happen if you give oral sex to someone who has genital herpes, which is more commonly caused by HSV-2 but can also be caused by HSV-1. In the same sense, you can pass HSV-1 or HSV-2 to someone through oral sex, causing lesions to appear on their genitals.

Even though you can get herpes from an asymptomatic person, the chance of getting infected is higher if you have contact with cold sores, especially when they’re oozing fluid.

What Are the Triggers for Cold Sores?

Some factors can trigger a repeat outbreak once the virus settles into your nerve cells, including:

• Health conditions that weaken your immune system

• Psychological stress

• Exposure to sunlight or wind

• Fatigue

• Hormonal changes

• Fever

• Dental work

• Cosmetic surgery

Risk Factors for Cold Sores

Though anyone, including children, can get a cold sore, some people have a higher risk of being infected with HSV viruses. For example, having a weak immune system and a partner with the virus both increase your risk.

According to one 2014 study, women have more annual cold sore outbreaks than men. Being white also increases your risk of getting cold sores.

Other risk factors for cold sores include:

• Obesity

• Smoking

• Playing contact sports

• Having cancer or HIV

Diagnosing Cold Sores

If you suspect you have a cold sore but you’ve never had one before, it’s a good idea to see your healthcare provider so they can test for HSV-1 and rule out other health issues.

Your provider can usually tell if you have a cold sore just by looking at it. If you have an open sore, they may swab it to test the fluid. Or they may take a blood test to check for HSV antibodies.

If you’ve had cold sores before and you’re pretty sure you’re having another outbreak, you may not need to see a healthcare provider. Outbreaks typically clear up on their own with the help of at-home care, although you will need to talk to a provider for prescription antiviral medicine, which we’ll discuss in the next section.

You may also want to see a provider for a cold sore if you:

• Develop a cold sore near your eye

• Have a cold sore that lasts beyond two weeks

• Have eczema

• Have a health condition that weakens your immune system

• Get cold sores more than five times a year

Cold Sore Treatments

The main treatments for cold sores include antiviral creams and pills, over-the-counter medication, and home remedies.

Antiviral Medications

Antiviral medications are either oral or topical, though oral medications are proven and effective. They can shorten the duration of an outbreak. Oral medications can also be used as a suppressive therapy to prevent recurrent outbreaks. For best results, you should start treatment as quickly as possible, ideally within 24 hours of your first symptoms. Always follow your provider’s guidance when taking the following medications.

Topical antiviral creams are typically applied to the affected area every two hours over the course of four days. They include:

• Acyclovir (Zovirax®)

• Penciclovir (Denavir®)

Patients typically prefer oral antivirals because they’re taken once or twice daily for one to seven days of treatment. They include:

• Acyclovir (Zovirax®)

• Valacyclovir (Valtrex®)

• Famciclovir (generic only)

Although these oral medications appear to be equally effective in reducing cold sores, especially when taken at the first sign of symptoms, the medication valacyclovir has some notable advantages.

For instance, valacyclovir has a longer duration of action and requires less dosing than other medications. You only need to take valacyclovir twice a day for one day, while acyclovir needs to be taken five times a day for five days of treatment.

When you first take valacyclovir, the medication starts working almost immediately and continues working in your body.

In a study comparing oral valacyclovir to acyclovir for oral herpes, researchers found valacyclovir was better absorbed than oral acyclovir, reducing the amount of time it took for sores to heal to a single day of treatment, which didn’t happen with oral acyclovir or topical creams.   

Learn more about valacyclovir here.

Are There Any Over-the-Counter Treatments for Cold Sores?

Some things you can try at home to deal with cold sores include:

• Over-the-counter ointments: Numerous non-prescription ointments for cold sores are available. They include docosanol (Abreva®) and lidocaine, which can reduce pain..

• Over-the-counter pain relievers: Medications like ibuprofen, acetaminophen, and aspirin can help reduce the pain and swelling of cold sores as well as associated symptoms like fever and body aches.

• Cold or hot compresses: Applying a cold or hot compress to sores may reduce swelling, itching, and discomfort.

How Do You Prevent Infections and Outbreaks?

To prevent cold sores and HSV infections and outbreaks, do the following:

• Explore suppressive therapy with antivirals if you have recurrent cold sores

• Avoid direct contact with open sores (no sex or kissing during outbreaks)

• Use sunscreen with SPF 30+

• Use condoms or dental dams during oral sex

• Avoid sharing utensils, razors, towels, and cosmetics that may come into contact with infected areas of the body

• Lead a healthy lifestyle to support your immune system

• Talk to a therapist if you deal with chronic stress

• Maintain a healthy weight

If you currently have a cold sore, reach out to a healthcare provider to get support.

Want more tips on how to deal with cold sores when they strike? Check out this guide to kissing and cold sores, find out how to stop a herpes outbreak with Valtrex, and review this herpes outbreak timeline.