Cold sores, also known as fever blisters, are a common viral infection caused primarily by the herpes simplex virus type 1 (HSV-1). In some cases, the herpes simplex virus type 2 (HSV-2), usually associated with genital herpes, can also cause cold sores, especially through oral-genital contact.

What causes cold sores?
Cold sores are highly contagious and easily transmitted from person to person, usually through contact with saliva or infected skin. Common ways the virus is transmitted include:

Direct contact: Kissing or sharing drinks, food, or utensils with an infected person.

Indirect contact: Using items contaminated with the virus, such as towels, lip balm, or cutlery.

Autoinfection (autoinoculation): Touching a cold sore and then touching other parts of the body, such as the eyes or genitals, can spread the virus.

Recognizing the Symptoms
Cold sores usually follow a series of stages:

Tingling or itching: A burning or itching sensation is usually the first sign, appearing 1 or 2 days before the sore develops.
Blister formation: Small, fluid-filled blisters develop, usually near the lips, but sometimes on the nose or gums.
Blister rupture: The blisters break open and form painful, red sores. This is the most contagious stage.
Scab formation: The sores dry and develop a scab, which eventually falls off during healing.

A typical outbreak lasts between 7 and 10 days. While the sores heal, the virus remains dormant in the body and can reactivate in response to certain triggers.

What triggers an outbreak? Several factors can reactivate the virus and cause new sores: