• Cold Sores
• Herpes
• Infections

Are Cold Sores Contagious?

Medically reviewed and edited by Dr. Lilliana Ramirez

Whether you call it a cold sore or a fever blister, oral herpes is a common infection of the mouth area that is caused by the herpes simplex virus type 1 (HSV-1).

According to Johns Hopkins Medicine, between 50% and 80% of American adults have oral herpes. Roughly 90% of adults have been exposed to the virus by age 50, says the National Institutes of Health.

Once infected, a person will have the herpes simplex virus for the rest of their life.

In this article, we will discuss what cold sores are, their causes, how long cold sores remain contagious, their symptoms, diagnosis and treatment, and how to prevent them.

What is a Cold Sore?

Cold sores, also known as fever blisters, are a very common viral infection. They are small, fluid-filled blisters that appear on and around your lips and mouth, or, in some cases, your cheeks and face.

These blisters often appear in patches. After the blisters open, a scab that lasts a few days will form.

Most cold sores will disappear in two to three weeks without scarring. However, there isn’t a cure for cold sores, so the only thing you can do is treat them.

Antiviral prescription pills or creams can help cold sores heal faster and may also cut down on the number, length, and severity of future cold sore outbreaks.

What Causes Cold Sores?

Cold sores are caused by the herpes simplex virus. There are two types:

Herpes simplex type 1 virus (HSV-1): This usually causes cold sores. Herpes simplex type 2 virus (HSV-2): This usually causes genital herpes.

Both forms of the virus’ sores look similar. It’s also possible for HSV-2 to cause sores on the mouth and for HSV-1 to cause sores on the genitals.

There are various ways to get cold sores. Some of these include:

• Kissing

• Sharing cosmetics

• Sharing food

• Oral sex (this applies to genital herpes as well)

Are Cold Sores Contagious?

Yes, cold sores are contagious. Transmission of HSV-1 occurs when someone with no prior infection comes in contact with:

• Herpetic lesions

• Mucosal secretions

• Skin that contains HSV-1

HSV-1 transmission typically occurs via oral-oral, oral-genital, or genital-genital contact, as well as contamination of skin abrasions with infected oral secretions.

There is a significant risk of getting infected by contact with contaminated saliva, such as sharing plates or cutlery. Even though the most common transmission is through direct contact with an active sore, the risk of contamination with contact with saliva is significant, even without active lesions.

However, even if you don't have blisters, you can still spread the virus. Many people who have the virus that causes cold sores don't show any signs or symptoms.

How Long are Cold Sores Contagious?

It usually takes roughly two weeks for a cold sore to no longer be contagious.

If you have a cold sore, waiting until all of your symptoms have gone away, including the blister and any scabs, will decrease the likelihood of spreading HSV to others. However, it doesn't eliminate the chances completely.

The idea that cold sores aren’t contagious once they’ve scabbed over is a misconception.

What triggers cold sores?

Fewer cold sore outbreaks mean that there is less risk of the infection spreading. As long as there is nothing that triggers the virus, it will stay inactive.

Everyone has different things that bring on a cold sore outbreak, but you can reduce your outbreaks by understanding and avoiding your own triggers.

Here are some common triggers for cold sores:

• UV light from the sun or sunbeds

• Emotional stress

• Fever and common colds

• An injury to the affected area

• Hormonal changes, such as those accompanying your menstrual cycle

Cold Sore Symptoms

When you contract the herpes simplex virus, your first cold sore usually appears quickly, between 2 and 12 days.

Tingling or burning on your lips and face may start several days before cold sores start to form. This is the best time to start treatment.

When the sore starts to form, you'll see a red, raised blister with a lot of fluid inside. If it is painful and tender when touched, there may be more than one cold sore.

Until the cold sore is dry and crusts over, the herpes virus is contagious.

During an outbreak, common cold sore symptoms include:

• Fever

• Muscle aches

• Swollen lymph nodes

You should call your doctor immediately if you develop any eye-related problems during a cold sore outbreak. In some cases, the herpes simplex virus can lead to permanent vision loss if not treated promptly.

How are Cold Sores Diagnosed?

Your doctor can often figure out if you have cold sores by just looking at the sores.

If the diagnosis isn't clear, they might take a sample of cells from the sore with a swab and examine them under a microscope.

A cold sore can look similar to other skin issues, such as:

• Pimples

• Blisters

• Canker sores

Cold Sore Treatment

While there is no cure for cold sores, there are several ways to treat them.

Here are a few treatments and medicines you can get over the counter or through your doctor to deal with a cold sore:

• Antiviral ointments, such as penciclovir (Denavir). Ointments tend to be most effective if they’re applied as soon as the first signs of a sore appear. They will need to be applied four to five times per day for four to five days.

• Over-the-counter creams, such as docosanol (Abreva). These creams can shorten an outbreak by anywhere from a few hours to a day. The cream must be applied several times per day.

How are Cold Sores Spread?

There are no full-proof methods to stop cold sores from spreading, but you can follow these simple steps to lower your chances of spreading it:

• Don’t touch your cold sores.

• Wash your hands regularly.

• Don't kiss anyone (even on the cheek).

• Avoid oral sex.

• Don't share personal items (such as food, eating utensils, straws, cups, glasses, lipsticks, lip balm, and even cold sore cream).

• Change your toothbrush.

Medications

Cold sores can also be treated with oral antiviral medications, such as:

• Acyclovir (Zovirax)

• Valacyclovir (Valtrex)

• Famciclovir (Famvir)

Keep in mind that these drugs are available by prescription only.

Your doctor may instruct you to take antiviral medications regularly if you’re experiencing complications with cold sores or if your cold sore outbreaks are frequent.

Home remedies for cold sores

Doctors recommend not applying any home remedies, because some, such as witch hazel, lemon extract, and aloe vera, can irritate the skin more and even further ulcerate the already ulcerated skin. These ulcerations can lead to scarring and delayed healing of lesions.

How Do I Get More Information About Cold Sore Treatment?

Because the cold sore virus is highly contagious and not curable, the condition is relatively common, particularly in older adults.

This means it's vital to speak with a doctor and to get tested right away if you think you've contracted cold sores or are showing any of the symptoms discussed here.

There are multiple kinds of medications that can keep the number of outbreaks and the severity of cold sores symptoms to a minimum.

To schedule a video appointment with a board-certifed doctor or nurse practitioner, head over to LifeMD.com.

Dr. Lilliana Ramirez

Dr. Ramirez is a licensed, board certified dermatologist. She received her medical degree from the University of Puerto Rico School of Medicine.

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