Cold sores are caused by a contagious virus called herpes simplex virus (HSV). There are two types of HSV. Type 1 usually causes oral herpes, or cold sores. Type 1 herpes virus infects more than half of the U.S. population by the time they reach their 20s. Type 2 usually affects the genital area.

Some people have no symptoms from the infection. But others develop painful and unsightly cold sores. Cold sores usually occur outside the mouth, on or around the lips. When they are inside the mouth, they are usually on the gums or the roof of the mouth. They are not the same as canker sores, which are not contagious.

There is no cure for cold sores. They normally go away on their own in a few weeks. Antiviral medicines can help them heal faster. They can also help to prevent cold sores in people who often get them. Other medicines can help with the pain and discomfort of the sores. These include ointments that numb the blisters, soften the crusts of the sores, or dry them out. Protecting your lips from the sun with sunblock lip balm can also help.

Both fever blisters and canker sores are common across all ages and can be painful. However, they are separate conditions with different causes. Read further to learn how to tell them apart and find out which treatments might help ease the pain.

Fever Blisters (also known as cold sores) are painful fluid-filled sores that form on the outside of the mouth around the lips. Fever blisters are very contagious.

Oral Herpes

Another common skin virus is herpes simplex virus (HSV). HSV has historically been divided into two types, HSV-1 and HSV-2. HSV-1 is typically transmitted by direct oral contact between individuals, and is usually associated with oral herpes. HSV-2 is usually transmitted sexually and is typically associated with genital herpes. However, both HSV-1 and HSV-2 are capable of infecting any mucous membrane, and the incidence of genital HSV-1 and oral HSV-2 infections has been increasing in recent years.

Infection by HSV-1 commonly manifests as cold sores or fever blisters, usually on or around the lips. HSV-1 is highly contagious, with some studies suggesting that up to 65% of the US population is infected; however, many infected individuals are asymptomatic. Moreover, the virus can be latent for long periods, residing in the trigeminal nerve ganglia between recurring bouts of symptoms. Recurrence can be triggered by stress or environmental conditions (systemic or affecting the skin). When lesions are present, they may blister, break open, and crust. The virus can be spread through direct contact, even when a patient is asymptomatic.

While the lips, mouth, and face are the most common sites for HSV-1 infections, lesions can spread to other areas of the body. Wrestlers and other athletes involved in contact sports may develop lesions on the neck, shoulders, and trunk. This condition is often called herpes gladiatorum. Herpes lesions that develop on the fingers are often called herpetic whitlow.

HSV-1 infections are commonly diagnosed from their appearance, although laboratory testing can confirm the diagnosis. There is no cure, but antiviral medications such as acyclovir, penciclovir, famciclovir, and valacyclovir are used to reduce symptoms and risk of transmission. Topical medications, such as creams with n-docosanol and penciclovir, can also be used to reduce symptoms such as itching, burning, and tingling.

This cold sore was caused by HSV-1. (credit: Centers for Disease Control and Prevention)

Viral Infections of the Skin and Eyes

A number of viruses can cause infections via direct contact with skin and eyes, causing signs and symptoms ranging from rashes and lesions to warts and conjunctivitis. All of these viral diseases are contagious, and while some are more common in children (fifth disease and roseola), others are prevalent in people of all ages (oral herpes, viral conjunctivitis, papillomas). In general, the best means of prevention is avoiding contact with infected individuals. Treatment may require antiviral medications; however, several of these conditions are mild and typically resolve without treatment. Chart below summarizes the characteristics of some common viral infections of the skin and eyes.

Infections by herpes simplex virus type 1 (HSV-1) frequently manifest as oral herpes, also called acute herpes labialis and characterized by cold sores on the lips, mouth, or gums. HSV-1 can also cause acute herpetic gingivostomatitis, a condition that results in ulcers of the mucous membranes inside the mouth (Figure). Herpetic gingivostomatitis is normally self-limiting except in immunocompromised patients. Like oral herpes, the infection is generally diagnosed through clinical examination, but cultures or biopsies may be obtained if other signs or symptoms suggest the possibility of a different causative agent. If treatment is needed, mouthwashes or antiviral medications such as acyclovir, famciclovir, or valacyclovir may be used.

(a) This cold sore is caused by infection with herpes simplex virus type 1 (HSV-1). (b) HSV-1 can also cause acute herpetic gingivostomatitis. (credit b: modification of work by Klaus D. Peter)

Did you know that the virus that causes “cold sores” or “fever blisters” on or around the mouth can also infect other areas of the body? The infection is caused by the herpes simplex virus. And it’s very common.

Most people with herpes infection don’t even know it. They may not have symptoms or not notice them.

For people who do have symptoms, a herpes infection may show up as one or more blisters. These can be on or near the mouth, eyes, genitals, or rectum. After the blisters break, they turn into sores or ulcers. These sores are painful and take about a week to heal.

Once someone is infected with herpes simplex, the virus goes into hiding and stays in the body for the rest of their lives. The virus can re-emerge at any time and cause an outbreak. Some people have outbreaks several times per year. Tingling or burning in the area can signal that an outbreak is looming.

There are two types of herpes simplex viruses: HSV-1 and HSV-2. HSV-1 is often transmitted during childhood. You can get it from close contact with someone who has the infection. For example, a family member with a cold sore may kiss a child. HSV-1 is the main cause of herpes of the mouth or eyes. Although it’s possible for HSV-2 to infect the mouth or eyes, it’s usually found in the genital area.

There’s no cure for herpes. But anti-herpes medicine can speed healing of the sores. If taken every day, this medicine can also lower the risk of future outbreaks.

“It’s the first episode that is particularly important to treat,” says Dr. Jeffrey I. Cohen, a herpes infection expert at NIH. That’s because the first outbreak is often the most severe. In addition to sores, you may have a fever and body aches. Also, the nearby lymph nodes might be swollen and painful.

A doctor may suspect a diagnosis of herpes from looking at a sore. But lab tests on a sample taken from the sore is needed to confirm the diagnosis. A blood test for HSV-1 and HSV-2 is also available to confirm if someone has been infected.

Researchers are working to develop herpes vaccines. “There are two different types of vaccines being developed for herpes virus,” Cohen explains. “One is a vaccine that would prevent infection in people who have not been infected with the virus.” Cohen’s research team at NIH is working on this type of vaccine.

“The other type of vaccine is for people who are already infected,” he says. “The idea is that we could boost their immune system so that they have fewer recurrences.”

The fact that most people don’t know that they’re infected makes vaccines especially important.

When someone is diagnosed with herpes, they may feel anger, sadness, or shame. They also may fear rejection by romantic partners.

Keep in mind that herpes outbreaks can be managed. People can lower the risk of infecting someone else by avoiding direct contact during an outbreak. For those with genital herpes, using anti-herpes medicine every day and condoms during sexual activity also reduces the risk of infection for a romantic partner.

Talk with your doctor if you have questions about preventing or managing herpes.

Help Fight the Stigma of Herpes

Don’t tell jokes with herpes as the punchline. And share the facts:

• Herpes infection is common.
• It may not cause any symptoms.
• Herpes can be spread by someone who doesn’t know they have it.
• You can get herpes in many ways, such as a kiss, sharing drinks or utensils, or sexual activity.
• Having herpes doesn’t mean you’re a bad person, immoral, or promiscuous.

Fever Blisters are caused by an infection with the herpes simplex virus, usually type 1, or HSV-1. It is estimated that nearly 90 percent of U.S. adults have been infected with the virus, although many people with the infection do not ever show symptoms. The virus generally resides in the nerve cells where it may periodically reactivate, traveling to the skin and causing recurring fever blisters.

Symptoms of fever blisters:

• Fluid-filled blisters on the outside of the mouth around the lips.
• Burning or tingling sensation at the site where the blisters will appear.
• And sometimes, fever, fatigue, or swelling of the lymph nodes, similar to other viral infections.

The main way to tell the difference between a fever blister and a canker sore is by location. Fever blisters occur outside the mouth, generally around the border of the lips. Canker sores occur inside the mouth.

They also differ in appearance: Fever blisters are patches of several small fluid-filled blisters, while canker sores are usually single round white or yellow sores with a red border.

Typically, both types of sores go away on their own and treatment is not usually required. There is no known treatment that can permanently cure fever blisters or canker sores and prevent them from recurring. Treatment focuses on minimizing the pain and speeding recovery time.

Fever blisters can be treated with prescription antiviral medications either applied as topical creams or taken orally. See a doctor if your cold sores persist longer than a few weeks, you develop a high fever, or you notice eye irritation.

Both fever blisters and canker sores can have triggers that produce flare ups. Try to identify and then avoid triggers so your flare ups become less frequent.

Tips for Fever Blisters

• Sun exposure may sometimes trigger outbreaks of fever blisters. If you have recurring blisters, using sunscreen may help reduce their frequency.
• Fever blisters are contagious. Avoid kissing, sharing eating utensils, cups, water bottles, or other items if you are experiencing symptoms.
• Be aware that in young children, fever blisters can cause loss of appetite, drooling, and fever that can last for several days.
• Talk to your doctor or your child’s pediatrician if symptoms are severe or recur frequently.