A herpes simplex lesion on the lower lip on the second day after onset. Image: CDC

Herpes simplex virus is mystifying, fascinating, and sneaky. Mystifying because we have yet to unravel all of its secrets; fascinating because when we do uncover one of its mysteries, we are amazed by the capabilities of such a tiny, microscopic object; and sneaky because it enters our bodies by stealth and conceals itself in our cells, taking us by surprise when it comes out of hiding and causes outbreaks of blisters and other lesions.

It can also be confusing. Herpes simplex virus actually comes in two flavors: HSV-1 and HSV-2. HSV-1 is associated more with oral herpes, which can cause “cold sores,” a type of blister that appears on the lips or face. HSV-2 is associated more with genital herpes, which can cause blisters and other lesions in the genital area. It used to be standard to describe HSV-1 as an “above-the-waist” infection and HSV-2 as a “below-the-belt” infection — but now many researchers are pointing out that it’s more appropriate to say that HSV-1 is both an orally and genitally transmitted infection while HSV-2 is a predominantly genitally transmitted infection. If HSV-1 enters the body in the genital area, it can cause a genital herpes infection — and likewise, if HSV-2 enters the body in the facial area, it can cause an oral herpes infection.

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Using condoms and dental dams during oral sex reduces risk of herpes transmission.

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What exactly is a cold sore, anyway? A cold sore, also known as a fever blister, is a cluster of blisters that can pop up around the lips or even in the mouth. Sometimes, cold sores are so painful that eating or drinking is difficult, and in extreme cases sufferers must be treated for dehydration. An especially severe infection could also cause high fever or swollen lymph nodes, and in young adults a first oral HSV-1 infection might be misdiagnosed as tonsillitis, possibly leading to unnecessary tonsillectomies. Most symptomatic first-time cold-sore outbreaks occur during childhood, and take about two or three weeks to clear up. Luckily, the first infection is almost always the most severe, and when the infection is reactivated it usually happens without symptoms.

Because both cold sores and genital herpes are caused by herpes simplex viruses, and because oral herpes is so common, many people are concerned that they might be more vulnerable to acquiring a genital herpes infection than they previously thought. They might have a lot of questions, and if they’ve sought answers to those questions, they might have heard a lot of conflicting answers. Let’s see what the scientific literature has to say.

• Can I get genital herpes if someone with cold sores performs oral sex on me?

Because HSV-1, the virus responsible for most oral herpes infections, can also cause genital herpes, many people wonder if someone with cold sores can transmit the virus to someone else by performing oral sex, resulting in a genital herpes infection. Other people wonder if HSV-1 can be transmitted via oral contact with the anus, resulting in a herpes infection in the rectal area. The answer to these questions is: Yes! Continue reading →