What Causes Herpes on Lips?

Oral herpes is usually caused by the herpes simplex 1 virus, or HSV-1. It spreads through intimate contact with an infected person through kissing and oral sex, but sharing cups, eating utensils, and other items can also pass along the virus.

Oral herpes — also known as cold sores or fever blisters — is a common viral infection of the mouth. Of all the adults in the U.S., it’s estimated that 50% to 80% have oral herpes. Roughly 90% of adults in the U.S. are exposed to herpes simplex 1, the virus that causes oral herpes, by the time they are 50 years old.

Once you have the virus, you will have it for your whole life. Outbreaks of sores may occasionally reoccur after you are initially infected, usually at times when you have low immunity, like when you have a cold or are very stressed. Exposure to extreme cold or heat and hormonal changes can also cause an oral herpes outbreak.

The symptoms of oral herpes vary and depend on whether you are experiencing your first outbreak or a subsequent occurrence.

First Outbreak

The first outbreak of oral herpes is usually much worse than subsequent outbreaks. During the first outbreak, you may get cold sores in and around your mouth. Some people also get them in their throat. During this preliminary outbreak, you may also have flu-like symptoms such as swollen lymph nodes, or you may just feel generally ill.

The outbreak of cold sores starts as fluid-filled blisters that are very contagious. After a few days, the blisters will leak fluid and become sores. The sores may last up to a week before they start to heal. 

Subsequent outbreaks

At least 25% of people who get oral herpes have a secondary outbreak after the first one. Subsequent outbreaks can include symptoms in the area where the cold sores will develop such as:

• Redness
• Swelling
• Itching
• Pain
• Burning

You will learn what getting a cold sore feels like for you. Subsequent outbreaks are usually much milder than the initial one.

Oral herpes is usually caused by the herpes simplex 1 virus, or HSV-1. Sometimes, however, herpes simplex virus type 2 (HSV-2) — the virus that usually causes genital herpes — can transmit to the mouth during oral sex, also causing oral herpes. The opposite is also true, as you can get HSV-1 on your genitals.

Herpes simplex 1 usually spreads through intimate contact with an infected person. People with active outbreaks are the most contagious, but there is always a small chance that a person can be contagious even without an outbreak.

HSV-1 is often passed through kissing and oral sex, but sharing cups, eating utensils, and other items can also pass along the virus.

You can reduce your chances of getting oral herpes by not kissing or having oral sex with someone who is having an active outbreak. Once their skin has healed and looks normal, you can resume intimate activities. 

Additionally, using a safer-sex barrier like a dental dam — a thin piece of latex that protects against direct mouth-to-genital contact during oral sex — can reduce the chances of getting oral herpes, regardless of whether a person has a current outbreak

Many diseases and conditions can cause sores on the mouth. Sometimes, doctors can make a diagnosis by visually examining the sores, though testing may also be necessary to get an accurate diagnosis. Doctors may perform a blood test or take a swab of the sores to find out whether it is herpes. The test can also determine whether it is HSV-1 or HSV-2.

There is no cure for either of the herpes viruses, and outbreaks may go away within a few weeks without treatment. However, you can manage outbreaks with prescription medication. These medicines make outbreaks less severe and shorter. Antiviral medications your doctor may prescribe include:

• Acyclovir (Zovirax)
• Famciclovir (Famvir)
• Valacyclovir (Valtrex)

Doctors recommend beginning these treatments as soon as you feel an outbreak coming on — before sores develop.

Topical ointments can also help symptoms fade faster.

If you do have an oral herpes outbreak, some things you can do at home to help with pain or discomfort include: 

• Using ice
• Applying a warm washcloth
• Washing blisters with soap and water
• Avoiding citrus
• Staying away from hot beverages
• Avoiding spicy foods
• Taking an over-the-counter pain reliever