Cold sore

A cold sore (also known as a fever blister, oral herpes, and herpes labialis) is a type of

About 2.5 per 1000 people are affected with outbreaks in any given year.[1] After one episode about 33% of people develop subsequent episodes.^[1] Onset often occurs in those less than 20 years old and 80% develop antibodies for the virus by this age.^[1] In those with recurrent outbreaks, these typically happen less than three times a year.^[10] The frequency of outbreaks generally decreases over time.^[1]

Terminology

The term labia means "lip" in

Signs and symptoms

Herpes infections usually show no symptoms;

Recurrent oral infection is more common with HSV-1 infections than with HSV-2. Symptoms typically progress in a series of eight stages:

1. Latent (weeks to months incident-free): The remission period; After initial infection, the viruses move to sensory nerve ganglia (trigeminal ganglion),^[1] where they reside as lifelong, latent viruses. Asymptomatic shedding of contagious virus particles can occur during this stage.
2. Prodromal
   (day 0–1): Symptoms often precede a recurrence. Symptoms typically begin with tingling (itching) and reddening of the skin around the infected site. This stage can last from a few days to a few hours preceding the physical manifestation of an infection and is the best time to start treatment.
3. Inflammation (day 1): Virus begins reproducing and infecting cells at the end of the nerve. The healthy cells react to the invasion with swelling and redness displayed as symptoms of infection.
4. Pre-sore (day 2–3): This stage is defined by the appearance of tiny, hard, inflamed papules and
   vesicles that may itch and are painfully sensitive to touch. In time, these fluid-filled blisters form a cluster on the lip (labial) tissue, the area between the lip and skin (vermilion border), and can occur on the nose, chin, and cheeks.^[17]
5. Open lesion (day 4): This is the most painful and contagious of the stages. All the tiny vesicles break open and merge to create one big, open, weeping ulcer. Fluids are slowly discharged from blood vessels and inflamed tissue. This watery discharge is teeming with active viral particles and is highly contagious. Depending on the severity, one may develop a fever and swollen lymph glands under the jaw.[18]
6. Crusting (day 5–8): A honey/golden crust starts to form from the syrupy exudate. This yellowish or brown crust or scab is not made of active virus but from
   immunoglobulins
   . This appears as the healing process begins. The sore is still painful at this stage, but, more painful, however, is the constant cracking of the scab as one moves or stretches their lips, as in smiling or eating. Virus-filled fluid will still ooze out of the sore through any cracks.
7. Healing (day 9–14): New skin begins to form underneath the scab as the virus retreats into latency. A series of scabs will form over the sore (called Meier Complex), each one smaller than the last. During this phase irritation, itching, and some pain are common.
8. Post-scab (12–14 days): A reddish area may linger at the site of viral infection as the destroyed cells are regenerated. Virus shedding can still occur during this stage.

The recurrent infection is thus often called herpes simplex labialis. Rare reinfections occur inside the mouth (intraoral HSV stomatitis) affecting the gums,

Oral HSV-2 shedding is rare, and "usually noted in the context of first episode genital herpes."[21] In general, both types can cause oral or genital herpes.^[22][23][24]

Cold sores are the result of the virus reactivating in the body. Once HSV-1 has entered the body, it never leaves. The virus moves from the mouth to remain latent in the central nervous system. In approximately one-third of people, the virus can "wake up" or reactivate to cause disease. When reactivation occurs, the virus travels down the nerves to the skin where it may cause blisters (cold sores) around the lips or mouth area.^[25]

In case of

People can transfer the virus from their cold sores to other areas of the body, such as the eye, skin, or fingers; this is called autoinoculation. Eye infection, in the form of conjunctivitis or keratitis, can happen when the eyes are rubbed after touching the lesion. Finger infection (herpetic whitlow) can occur when a child with cold sores or primary HSV-1 infection sucks their fingers.^[29][30]

Blood tests for herpes may differentiate between type 1 and type 2. When a person is not experiencing any symptoms, a blood test alone does not reveal the site of infection. Genital herpes infections occurred with almost equal frequency as type 1 or 2 in younger adults when samples were taken from genital lesions. Herpes in the mouth is more likely to be caused by type 1, but (see above) also can be type 2. The only way to know for certain if a positive blood test for herpes is due to infection of the mouth, genitals, or elsewhere, is to sample from lesions.^[31][32] This is not possible if the affected individual is asymptomatic. The body's immune system typically fights the virus.^[33]

Prevention

Primary infection

The likelihood of the infection can be reduced through avoidance of touching an area with active infection and contact sports and frequent

Treatment recommendations vary on the severity of the symptoms and chronicity of the infection. Treatment with oral antivirals such as acyclovir in children within 72 hours of illness onset has shown to shorten duration of fever, odynophagia, and lesions, and to reduce viral shedding.^[35][1] For patient with mild to moderate symptoms, local anaesthetic such as lidocaine for pain without antiviral may be sufficient. However, those with occasional severe recurrences of lesions may use oral antivirals.^[1][35] Patients with severe cases such as those with frequent recurrences of lesions, presence of disfiguring lesions, and serious systematic complications may need chronic suppressive therapy on top of the antiviral therapies.^[35][1]

Mouth-rinse with combinations of ethanol and essential oils against herpes as therapeutic method is recommended by the German Society of Hospital Hygiene.^[43] Further research into virucidal effects of essential oils exists.^[44][45]

Epidemiology

Herpes labialis is common throughout the world. A large survey of young adults on six continents reported that 33% of males and 28% of females had herpes labialis on two or more occasions during the year before the study. The

Research has gone into vaccines and drugs for both prevention and treatment of herpes infections.^{[47][48][49][50][51][52]}

References