Can I Get Genital Herpes If I Have Oral Sex With Someone Who Has a Cold Sore?

Cold sores (sometimes called fever blisters) and genital herpes are both caused by a herpes virus, cause skin lesions, and are highly contagious. They are also both spread by skin-to-skin contact. If you kiss someone with a cold sore, you're at risk of developing one yourself. And if you have sexual intercourse with a partner who has genital herpes, you can become infected as well.

And yes, it's also possible to develop genital herpes if someone with a cold sore performs oral sex on you.

This article provides a broad overview of cold sores and genital herpes, explains how one can cause the other, and offers guidance for preventing genital herpes infections when one sexual partner has a cold sore.

Comparing Cold Sores and Genital Herpes

A cold sore (herpes labialis) is a cluster of tiny fluid-filled blisters that usually form on one side of the lips. Most people can tell when a cold sore is coming on: The area will feel tingly or itchy just before the lesion pops up. These sensations are known as prodromal symptoms.

Cold sores break open easily. When they do, the clear fluid inside oozes out and the blister forms a crust. Most go away after a week or two.

Genital herpes (herpes genitalis) lesions are clusters of blisters that may be preceded by pain or tingling. Lesions can form on or inside the vagina of females, on the penis or scrotum of males, and around the anus, thighs, or buttocks of people of either sex.

The Herpes Virus

Cold sores and genital herpes are both caused by a herpes virus. Most cold sores are caused by herpes simplex 1 (HSV-1); genital herpes is most often caused by herpes simplex 2 (HSV-2).

However, sometimes genital herpes infections can be caused by HSV-1. An HSV-1 infection on the lips of one person can spread to the genitals of another person during oral sex, causing an HSV-1 infection.

In fact, some scientists estimate that more than half of new genital herpes infections are caused by HSV-1 rather than HSV-2.

There's evidence that HSV-1 may be more infectious than HSV-2. That means that penile or vaginal oral sex given by a partner who has a cold sore may be riskier than genital-to-genital contact or penetrative sex with a partner who has HSV-2 genital herpes.

Although not nearly as common, it is possible for a genital HSV-2 infection to be transmitted to a person's mouth—in other words, a cold sore on the lips could develop if you perform oral sex on someone with genital herpes.

It's important to be aware that both cold sores and genital herpes can be transmitted from one person to another even when there are no obvious lesions. This is known as asymptomatic shedding.

Prevention and Management

The same measures that help prevent a herpes infection during genital-to-genital contact can help prevent infection of the genitals from a cold sore.

Abstain

If your partner has a cold sore, the only way to guarantee you don't get infected from contact with it is to avoid oral sex until the lesion has cleared up completely.

Someone who has a cold sore can pass herpes to you, which means you can end up passing it back to them, back and forth.

It's also best not to even kiss or share a toothbrush, coffee cup, water bottle, or eating utensils.

Use a Condom

Neither a male condom nor a female condom will completely eliminate the risk of spreading the herpes virus from a cold sore to another person's genitals, but it will provide some protection when used correctly.

Make sure the condom you use is approved by the U.S. Food and Drug Administration (FDA) for protecting against STDs.

Medication

Anti-viral drugs such as Valtrex (valacyclovir) and Zovirax (acyclovir) help prevent the virus from reproducing and shedding (releasing new cells that can spread the infection), which lowers the risk that your partner can pass herpes on to you.​

These medications also help reduce frequent outbreaks.

Get Tested

Herpes testing isn't a standard part of sexual health care. However, if you believe you've been exposed to herpes and want to know what your status is, ask your healthcare provider for a test.

You also may want to be tested if you're at risk for herpes infection.

According to the National Institutes of Health, you could be at risk if you:

• Have lesions that look like herpes on any part of your body
• Have had sex with someone who has herpes
• Are pregnant and you or your partner have herpes symptoms or have had a herpes infection in the past
• Have more than one sex partner
• Are a man who has sex with men
• Have a partner with HIV and/or another sexually transmitted infection (STI), as having HSV-2 increases your risk of becoming infected with other STIs

Testing may involve swabbing fluid and cells from a lesion or taking a sample of blood from a vein. Both types of samples are then tested for the virus in a lab. Some blood tests are designed to identify specific types of herpes virus, but they are not 100 % accurate. 

Summary

Cold sores and genital herpes are both caused by herpes viruses. Cold sores most often are associated with HSV-1, while genital herpes is associated with HSV-2. And HSV-1 can be transmitted from one person's mouth to another person's genitals during oral sex.

Prevention includes abstaining from oral sex, using condoms, taking medication to suppress the herpes virus, and getting tested.