Cold Sore (Herpes Labialis)

Cold sores, also known as fever blisters, oral herpes, or herpes labialis, are a common infectious disease of the lip caused by the herpes simplex virus (HSV). The condition is characterised by small blisters or sores that typically heal within ten days. The virus, usually HSV type 1 (HSV-1), remains dormant in the trigeminal ganglion and can periodically reactivate.

Signs and Symptoms

Herpes labialis usually presents with burning pain followed by the development of small blisters or sores. Initial infection may also include symptoms such as fever, sore throat, and enlarged lymph nodes. Recurrent infections follow a series of stages:

1. Latent: Virus resides in sensory nerve ganglia without symptoms.
2. Prodromal: Tingling and redness precede blister formation.
3. Inflammation: Swelling and redness as the virus reproduces.
4. Pre-sore: Formation of tiny, inflamed papules and vesicles.
5. Open lesion: Vesicles break open, creating a weeping ulcer.
6. Crusting: Formation of a honey/golden crust as healing begins.
7. Healing: New skin forms under the scab.
8. Post-scab: Red area remains as the cells regenerate.

Causes

Herpes labialis is primarily caused by HSV-1 and occasionally by HSV-2. The infection spreads through direct contact with infected individuals, often via non-sexual means. Triggers for reactivation include sunlight, fever, psychological stress, and menstruation. The virus resides in the central nervous system and can reactivate to cause cold sores.

Diagnosis

Diagnosis is usually based on clinical symptoms but can be confirmed with specific testing. Differential diagnoses include herpangina, aphthous stomatitis, impetigo, and mononucleosis.

Prevention

Primary prevention involves avoiding direct contact with infected areas and frequent hand washing. During active infections, it is advised to avoid kissing and sharing personal items. For recurrent infections, sun protection and antiviral medications such as acyclovir and valacyclovir may help reduce frequency and severity.

Treatment

Treatment options vary based on symptom severity and include:

• Topical Creams: Zinc oxide, anaesthetic (lidocaine, prilocaine), and antiviral (acyclovir, penciclovir) creams.
• Oral Antivirals: Acyclovir, valacyclovir, and famciclovir, effective in reducing symptom duration and viral shedding.
• Mouth Rinse: Combinations of ethanol and essential oils have shown therapeutic potential.

There is no cure for HSV, but the body's immune system typically manages the virus. Chronic suppressive therapy may be necessary for severe or frequent recurrences.

Epidemiology

Herpes labialis is widespread globally. Studies indicate varying lifetime prevalence rates, such as 20-45% in the USA, 32-42% in France, and 32% in Germany. Recurrence rates are common, with around 33% of individuals experiencing subsequent episodes.

Research

Ongoing research aims to develop vaccines and new therapeutic drugs for both prevention and treatment of herpes infections.

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Self-assessment MCQs (single best answer)

What is the primary cause of cold sores?

Which stage of herpes labialis involves the formation of tiny, inflamed papules and vesicles?

What symptom is typically experienced during the prodromal stage of herpes labialis?

Which of the following is NOT a common trigger for the reactivation of herpes labialis?

What is the recommended primary prevention method for herpes labialis?

During which stage of herpes labialis does the formation of a honey/golden crust occur?

What are the common symptoms of the initial herpes labialis infection?

Which diagnostic method is commonly used to confirm herpes labialis?

Which of the following treatments is NOT used for herpes labialis?

What is the estimated lifetime prevalence of herpes labialis in the USA?