Oral herpes: everything you need to know about cold sores.

Cold sore: what exactly is it?

The cold sore, also known as labial herpes, is a very common viral infection caused by the herpes simplex virus type 1 (HSV‑1). It usually appears on the lips, at the junction between the skin and the mucous membrane, but can also occur around the mouth or the nose. The lesions often take the form of a small cluster of blisters filled with clear fluid, lying on an area of skin that is red and slightly inflamed. These blisters eventually rupture, after which a scab forms before the skin heals completely.

The appearance of a cold sore is often preceded by early warning signs, known as prodromes.

Several hours to two days before the eruption, it is common to experience tingling, a burning sensation and/or itching on a small area of the lips. The vesicles then appear rapidly and the episode usually progresses over 7 to 10 days before resolving spontaneously. Although benign in the majority of cases, cold sores are contagious for as long as the lesions are present, because the fluid contained in the vesicles is rich in viral particles. Saliva, via a shared kiss, a handshake, or the sharing of cutlery or glasses, are all situations that facilitate the transmission of herpes labialis.

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3.8 billion

of people under the age of 50 are carriers of HSV-1.

64%

of the global population carries HSV-1.

What is the origin of cold sores (oral herpes)?

The majority of the population carries the herpes simplex virus type 1, which is often contracted in childhood through direct contact with an infected person.

After this primary infection, the virus does not disappear: it remains in the body in a latent state, lodged in certain nerve ganglia located near the infected area. Most of the time, it stays silent, but it can become reactivated from time to time, which leads to the appearance of a cold sore.

Several factors can promote this viral reactivation. A reduction in immune defences, linked for example to fatigue, stress, an infection accompanied by fever, or certain immunosuppressive treatments, may trigger an episode of cold sore (herpes labialis). Other factors are also known to favour recurrences, such as significant sun exposure, hormonal fluctuations, local trauma, for example after dental treatment, or irritation of the skin. During the active phase of the outbreak, the cold sore is highly contagious and can easily be transmitted to people nearby.

How can a cold sore be treated?

In most cases, a cold sore heals spontaneously within 7 to 10 days.

The main aim of treatment is therefore to relieve symptoms and to limit the duration of the episode of herpes. At the first warning signs — tingling, burning sensations, or itching — it is possible to apply topical antiviral treatments, generally in the form of a cream containing aciclovir or penciclovir. These medicines work by slowing down viral replication and can slightly reduce the duration of the episode if they are used sufficiently early.

Cold sores: best practices.

Avoid touching the lesions, as the fluid contained in the vesicles is rich in virus and may promote the spread of the infection to other areas of the skin, particularly the eyes.
Wash your hands regularly, especially after applying a treatment to the cold sore.
Do not pierce the blisters or remove the scab, as this may slow down the healing process.
Avoid close contact, such as kissing, especially with infants and immunocompromised individuals, who are more vulnerable to virus‑related complications, and do not share items that may come into contact with the mouth (glasses, cutlery, towels, toothbrushes, etc.).
Protect your lips from the sun, as exposure to UV rays can promote recurrences.
Begin local treatments at the first signs, in order to limit the progression of the flare.

In certain cases, particularly when flare-ups are frequent, extensive or especially painful, an oral antiviral treatment may be prescribed by a doctor. Agents such as aciclovir, valaciclovir or famciclovir can then help to reduce the intensity and duration of the episode. At the same time, a few simple measures can help to limit discomfort: avoiding touching the lesions, keeping the area clean and dry, and protecting the lips from the sun with a balm with an SPF. If symptoms are severe, persist for more than about ten days, or occur in someone who is immunocompromised, it is important to consult a healthcare professional.

When should you consult a doctor for a cold sore?

Contact your doctor in the following days if:

You are unsure about the nature of the lesions present on the lips or around the mouth.
The flare-up is more severe than usual.
The cold sore is spreading or has not healed after 10 days.
Recurrences are frequent (more than six episodes per year).

Consult your doctor during the day if:

The cold sore is accompanied by a high fever or significant pain.
You are experiencing eye symptoms in addition to the lesions (eye pain, redness, sensitivity to light), which may suggest a herpetic keratitis.
You are immunocompromised.