Cold Sore

What Are Cold Sores?

Cold sores are highly contagious, painful blisters that appear on the mouth. They can appear alone or in clusters and usually clear up on their own after 2-4 weeks. Cold sores are estimated to affect between 50-90% of the adult US population.

What Causes Cold Sores?

Cold sores are caused by the herpes simplex virus, and most commonly by a specific strain known as HSV-1. The other strain (HSV-2) is the one that usually causes genital herpes, although this is not true in every case.

Cold sores are not exclusively an STI and can be caught from any type of skin-to-skin contact. Kissing and oral sex can spread the herpes simplex virus but so can sharing items like lipstick and food.

It is estimated that at least 50% of American adults have the cold sore virus in their bodies, but only a portion of them ever show symptoms.

Whether the carrier shows symptoms or not, the virus can be passed on to the people they come into close contact with. While anyone can catch it, children under 3 years old are most susceptible to infection.

Common Cold Sore Triggers


Symptoms that suggest you might have a cold sore:

Tingling or itchy lips


Crusty sores around mouth

Oozing fluid around mouth


Cold Sore Stages

Cold sores typically follow these 5 stages:
Stage 1: Tingling and Itching

Before you even see a sore, you might feel it coming on. This will be a tingly, itchy feeling around your mouth. Even if you can’t see it yet, you could still pass on the herpes simplex virus at this stage.

Stage 2: Sores appear

When a cold sore first appears, it will be red, smooth and filled with fluid. This fluid contains the herpes simplex virus, so you should not attempt to burst a cold sore yourself.

Stage 3: Sores burst and ooze, becoming very painful

When the cold sore bursts, the fluid inside will seep out and the sore will be red and flat. This infectious fluid will now be on the surface of your skin, so you should be careful not to touch other areas of your body after touching your mouth.

Stage 4: Sores dry out, scab over and remain painful

The cold sore will then dry out and form a crust, which will look anywhere between yellow and dark red. During this time, you still have a high chance of passing the virus on to yourself and others.

Stage 5: Scabs fall off leaving unbroken skin

Once the scabs fall off completely, the cold sore is healed and you are no longer infectious.

  • treatable