Cold Sores: Causes

Cold sores are the most common form of infection caused by the herpes simplex virus: most adults on the planet have it. The outbreak itself usually heals within 10 days, but the virus stays in the body forever and reminds you of itself from time to time. Below is what is known about the causes and what is not.

What cold sores are

Herpes simplex is a viral disease with a characteristic eruption of grouped vesicles on the skin and mucous membranes. It is caused by two types of the virus: HSV-1 and HSV-2. The labial, that is, lip, form is the most common; in everyday life it is called a "cold sore on the lips," although it has nothing to do with acute respiratory viral infections.

The scenario is typical: first tingling, itching, or burning, and within the next 48 hours one or more painful fluid-filled vesicles appear on the face. They burst and become covered with a crust, and everything heals on average within 10 days. A person is contagious from the moment of the first tingling until complete healing. Similar symptoms occur with a boil, a mouth ulcer, and impetigo — these are other conditions.

Where the herpes simplex virus comes from

Most people encounter the virus in childhood — through close skin contact, for example a kiss, with a person who has an outbreak. Transmission occurs through direct contact with damaged tissues or biological fluids; it is also possible through the skin during asymptomatic carriage.

After infection, the virus integrates into the genome of the host cell, enters nerve endings, and travels along them to a sensory neuron in a ganglion, where it enters a latent stage. The immune system does not eliminate it — which is why outbreaks return. The global prevalence of herpes simplex viruses as of 2009 was estimated at 65–90%. In the USA in 2006, HSV-1 was present in 57.7% of people and HSV-2 in 16.2%, and only 18.9% of those seropositive for HSV-2 knew about their infection.

Outside the body, the virus remains active for about a day at room temperature and normal humidity, and on metal surfaces for up to 2 hours.

What causes cold sores: triggering factors

An outbreak does not arise "from scratch": by that time the virus is already living in the body. A recurrence is triggered by reactivation of the latent infection. Among the triggers cited by doctors are illness, sun, and menstruation.

HSV-1 more often causes lesions of the mouth, neck, face, and eyes, while HSV-2 causes anogenital ones. However, both types can cause outbreaks in both locations, for example after orogenital contact.

Why cold sores occur frequently and whether they appear on the body

In most people, exacerbations occur several times a year, and over time less often. After several years, recurrences may be asymptomatic, but the person remains contagious nonetheless. The likelihood of recurrence is higher with immunodeficiencies (HIV infection, tumors, organ transplantation). There is no drug that completely eliminates the virus from neurons: existing ones only suppress its replication.

Besides the lips, the virus affects the face, shoulders, limbs, and the genital area. Herpetic whitlow on the fingers, herpes gladiatorum in wrestlers, ocular herpes (keratitis), herpetic encephalitis and meningitis, and neonatal herpes have been described. In recurrent genital herpes, HSV-2 is detected in 95% of cases.

When to see a doctor

Herpes can be diagnosed with laboratory methods: virological testing of the contents of the outbreak (culture) and detection of antibodies to the virus in the blood. You should make an appointment with a doctor if:

• the outbreak has not begun to heal within 10 days;
• it is very large or very painful;
• you or your child have swollen, painful gums and ulcers in the mouth (gingivostomatitis);
• immunity is weakened — for example, due to chemotherapy or diabetes;
• there is doubt that this is herpes and not another disease.

Newborns, pregnant women, and people with weakened immunity may be referred to a hospital for consultation or treatment.

An outbreak on the lip by itself is not a reason to call an ambulance; 103/112 — for general emergency signs that threaten life, for example signs of a stroke or heart attack.

This material is for reference: it explains the mechanism and triggers but does not replace a doctor's consultation, which will assess your specific situation.

This content is for reference and does not replace a doctor's consultation. Medical disclaimer