Cold sores (oral herpes simplex) Definition, Causes, Symptoms, Diagnosis and Treatment.

Cold sores (oral herpes simplex)

A cold sore  is a painful and unsightly, though not  normally serious, recurrent virus infection of the  area  around the  lips.

Causes

Cold  sores are caused by the  herpes simplex virus type 1 (HSV-1).
Transmission of infection is through transfer of the  virus via saliva to mucous membranes, e.g. by kissing.
The  infection is usually contracted in childhood; it may  not  manifest clinically for several years or at all,  but  the  virus is never eliminated from  the  body.
Following attacks, the  virus regresses to the  ganglia of the  trigeminal and lumbosacral nerves, where it lies  dormant until one  of several trigger factors or lowered immunity allows it to break out  again.
Attacks are frequently triggered by the  common cold, hence the  common name of the  condition. Outbreaks also  often follow exposure to the  sun, giving rise  to the  other common name, sun blisters.
Other trigger factors include: fatigue; stress; exposure to cold weather and wind; trauma around the  mouth; hormonal changes associated with the  menstrual cycle.

Epidemiology

Cold  sores are very  common: about 80% of the  population are asymptomatic carriers of the  virus, and 20–25% of these (about 8 million people) suffer, on average, two  symptomatic outbreaks per  year.

Signs  and symptoms

Outbreaks may  begin with a prodromal phase of up  to 24 hours before any visible signs appear, during which the  area  on or around the  lips begins to tingle, burn or itch.
Erythema then develops, followed by the  formation of painful and irritating fluid-filled blisters on the  lips and skin around the  mouth, which break down
into shallow, weeping ulcers within 1–3 days.

The  ulcers dry  and form  crusts, which are shed, and the  area  heals within a further 2 weeks.
The  total length of an episode is usually 10–20 days.
Initial outbreaks in children typically manifest as gingivostomatitis, with lesions all over  the  inside of the  mouth and symptoms of systemic infection. Primary infection in adolescents manifests as pharyngitis, with lesions in the throat and symptoms similar to glandular fever.

Differential diagnosis

Mouth ulcers: these occur on the  mucous membranes and tongue inside the mouth, not  on the  outside of the  lip  and mouth.
Chickenpox: vesicles can  occur both around the  outside and inside the  mouth, but they are also  widespread on other parts of the  body.
Impetigo: a bacterial skin infection, more common in children, that usually affects the  face but  can  spread more widely. Lesions are itchy and not  confined to the  area  round the  lips, although they may  first appear there.
Lip cancer: lesions develop slowly and are initially painless.
Primary chancre of syphilis: sores can  occur on the  lip.  A single hard ulcer appears, which is painless, followed by swelling and hardening of lymph glands in the  neck, then spreading to lymph glands elsewhere in the  body.
Angular cheilitis: cracks occurring at the  corners of the  mouth that become inflamed and macerated. It is most common in elderly denture wearers.

Symptoms  and circumstances for referral

young children and babies
sores that do not  heal within 14 days
painless sores
multiple sores
systemic symptoms
frequent attacks
any  eye involvement. HSV in the  eyes  can  cause herpes simplex keratitis, a potentially sight-threatening infection
atopic and immunocompromised patients.

Treatment

Cold  sores are difficult to treat – even systemic antiviral therapy has  not  proven particularly effective. Non-prescription treatments are the  antiviral agents, aciclovir and penciclovir, and preparations for symptomatic relief containing antiseptics, astringents and local anaesthetics.

Aciclovir
Aciclovir is presented as a 5%  cream.

Cold sores (oral herpes simplex)

Aciclovir is a synthetic analogue of guanine. Its spectrum of activity is specific to human pathogenic viruses that produce thymidine kinase, of which HSV-1  is one.
Aciclovir is converted by thymidine kinase within viral cells to aciclovir triphosphate, which is then incorporated into viral DNA instead of the deoxyguanosine triphosphate required for DNA synthesis and replication.
The  cream is applied five times daily, at 4-hourly intervals, starting, if possible, as soon as prodromal symptoms occur. Treatment can  be continued for up  to 10 days, if necessary.
Evidence of the  effectiveness of topical aciclovir has  not  been convincing, but it may  shorten attacks by a day  or two  if use  is begun early enough.
There is limited evidence that aciclovir cream reduces recurrence of cold sores, but  little proof that it protects against attacks caused by ultraviolet radiation, one  of the  most common triggers of the  condition.
Aciclovir cream is licensed for use  in children and pregnant women.

Penciclovir
Penciclovir is available as 1%  cream.
Its antiviral activity and effectiveness are similar to that of aciclovir.
It is applied 2-hourly during waking hours.

Other preparations
Products containing combinations of constituents with local anaesthetic and analgesic effects, such as lidocaine, choline salicylate and phenol, counterirritants such as ammonia solution and menthol, and astringents such as zinc sulphate and tannic acid, are  marketed to reduce discomfort and promote faster healing of sores while the  infection takes its  course. Some are  formulated with alcoholic bases, which may  have a drying effect  on  sores and speed up healing. The  bland cream bases of some products may  have a soothing effect.
Combination preparations for cold sores are  relatively innocuous. Creams
can  be applied as frequently as necessary, although lotions and gels  are  limited to three or four  applications per  day.

Additional  advice

To prevent spread of infection to the  eyes:
– patients should wash their hands after  applying treatment
– women should be very  careful when applying eye makeup if they have a cold sore.
To prevent spread of infection to others, people with cold sores should not share towels, face flannels and cutlery with others.
For sufferers whose attacks are triggered by sunlight, an ultraviolet-blocking lip salve or high-factor sunscreen is an effective prophylactic