logo Viral skin infections

Skin infections

Viral skin infections

Objectives

  • Be able to identify and manage common viral skin infections.
  • Be familiar with the range of appearance of viral infections.

Key points

Key points include:

  • Warts are due to more than 120 subtypes of human papillomavirus.
  • The primary lesion for a wart is a hyperkeratotic papule.
  • Wart paint containing salicylic acid is suitable treatment for most viral warts.
  • Molluscum contagiosum is due to a pox virus.
  • The primary lesion for molluscum contagiosum is an umbilicated papule.
  • Molluscum papules are most often found in skin flexures.
  • Molluscum contagiosum often provokes localised eczema.
  • Herpes simplex type 1 infection most often presents as recurrent herpes labialis (cold sores).
  • Herpes simplex type 2 infection most often presents as recurrent herpes genitalis.
  • Primary infection may be asymptomatic or present as severe blistering with regional lymphadenopathy, fever and malaise.
  • The primary lesion for herpes simplex is an umbilicated vesicle.
  • Severe herpes simplex infection is treated with oral acylovir 200mg five times daily for 5 days.
  • Herpes zoster is reactivated varicella in a localised dermatomal distribution.
  • Herpes zoster results in pain, crops of vesicles and pustules and general malaise.
  • Postherpetic neuralgia (>1 month after active zoster) is more common in the elderly.

Viral warts

Viral warts are tumours or growths of the skin caused by infection with Human Papilloma Virus (HPV); more than 120 subtypes are known. Viral warts are particularly common in childhood (affecting about 15% of school children) and are spread by direct contact or auto-inocculation. Characteristically they are hyperkeratotic "verrucous" papules. They are frequently painful and they cause significant embarrassment. Quadrivalent vaccine prior to onset of sexual activity protects against HPV 6, 8, 16 and 18 in males and females.

Exophytic wart

Common wart

Filiform wart

Koebnerised plane wart (arising in the line of minor trauma)

Mosaic warts (clustered in a mosaic-like plaque)

Myrmecia (inwardly growing)

Plane (flat) warts

Periungual warts

Condyloma acuminata (genital warts)


Genital warts are often transmitted sexually. Types 6 and 8 are the most common to cause symptoms but types 16 and 18 predispose to cervical, penile and vulval cancer.

In children, even without treatment, 50% of warts disappear within 6 months; 90% are gone in 2 years. They are more persistent in adults but in most they clear up eventually.

Many people don't bother to treat them because treatment can be more uncomfortable and troublesome than the warts - they are hardly ever a serious problem.

Wart removal may stimulate an immune response, if not, recurrence is likely.

The most popular treatments include:

How to use wart paint

Apply wart paint once daily. Persevere for twelve weeks or longer - up to 70% of warts will resolve with wart paints, and others feel more comfortable because the keratinised surface has been removed.

First, the skin should be softened in a bath or bowl of hot water. The hard skin should be rubbed away from the wart surface with a piece of pumice stone or emery board. The wart paint or gel should be applied accurately, allowing it to dry. It works better if covered with plaster or duct tape (particularly recommended when the wart is on the foot).

If the chemical makes the skin sore, stop treatment until the discomfort has settled, then recommence as above. Take care to keep the chemical off normal skin.

Other measures may include:

Molluscum contagiosum

Molluscum contagiosum is a common cutaneous infection mainly presenting in childhood as multiple soft umbilicated papules in the flexures. Molluscum often provokes localised eczema. As the lesions resolve they may become inflamed or necrotic and may leave punctate scars. The cause is a pox virus. The papules resolve after a few months and rarely persist for longer than a year. Thick white material (molluscum bodies) can be expressed from the papules, which hastens their resolution.

Molluscum contagiosum

Localised eczema due to molluscum contagiosum

Scarring from recently resolved molluscum contagiosu


Treatment may include:

Herpes simplex

Herpes simplex virus (HSV) type 1 mainly affects the face and type 2 mainly affects genital skin, although in 10% of infections the reverse is true and any mucocutaneous site may be affected.

The virus is inoculated into the affected area and is more likely with minor injury, e.g. facial lesions contracted in rugby ("scrum pox"). Primary type 1 HSV infections occur mainly in infants and young children, and are usually mild or subclinical but may result in severe ulceration, oedema, regional lymphadenopathy and systemic symptoms. Type 2 infections occur mainly after puberty, often transmitted sexually.

Both type 1 and type 2 herpes simplex viruses reside in a latent state in spinal anterior horn cells. Recurrences are due to proliferation of virus within the epidermis of the affected dermatome and present as clusters of 2-3mm umbilicated clear or haemorrhagic vesicles. These persist for 5 to 10 days and are typically preceded by localised tingling or burning. Mild fever and malaise may occur. Asymptomatic viral shedding is also common.

Following the initial infection immunity develops but does not fully protect against further attacks in the same or new sites. However where immunity is deficient, both initial and recurrent infections tend to recur more frequently and to be more severe.

Herpetic gingivostomatitis

Recurrent herpes labialis (cold sores)

Recurrent facial herpes

Eczema herpeticum (severe herpes simplex infection in an individual with atopic dermatitis)

Genital herpes

Child with primary herpes (mother had concurrent cold sore)


Complications may include:

Recurrent herpes infections can be triggered by:

The diagnosis may be confirmed by one of the following methods:

Treatment may include acyclovir for acute severe infections and prophylaxis. This may be required short term to cover facial surgical or cosmetic procedures or parturition, or long term in those with frequent recurrences.

Herpes zoster

Shingles is a painful blistering rash caused by reactivation of Herpes zoster. The primary infection presents as chickenpox (varicella) usually during childhood. Like herpes simplex, the virus persists in the anterior horn cells before it is reactivated. This can occur in childhood but is much more common in adults, especially the elderly, sick or immune suppressed. Shingles patients are infectious (resulting in chickenpox in those who have never developed primary immunity), both from virus in the lesions and in some instances the nose and throat.

The first sign of zoster is usually pain, which may be severe, in the areas of one or more sensory nerves, often where they emerge from the spine. The patient usually feels quite unwell with fever, headache and regional lymphadenopathy. Within one to three days of the onset of pain, crops of closely grouped erythematous papules develop within the unilateral dermatome(s). New papules continue to appear for several days, each blistering or becoming pustular then crusting over. The pain and general symptoms subside gradually as the eruption disappears. In uncomplicated cases recovery is complete in 2-3 weeks in children and young adults, and 3 to 4 weeks in older patients.

The thoracic, cervical, ophthalmic and lumbar/sacral sensory nerve supply regions are most commonly affected at all ages but the frequency of ophthalmic shingles increases with age. Rarely the eruption may affect both sides of the body.

Zoster vesicles

Ophthalmic zoster

Ophthalmic zoster

Mandibular zoster, affecting tongue

T2 zoster

T5 zoster


In elderly and undernourished patients the blisters are deeper. Healing may take many weeks and be followed by scarring. Muscle weakness arises in about one in twenty patients because the muscle nerves are affected as well as the sensory nerves. Facial nerve palsy is the most common result. There is a 50% chance of complete recovery and in time some improvement can be expected in nearly all cases.

Post-herpetic neuralgia is defined as persistence or recurrence of pain more than a month after the onset of shingles. It becomes increasingly common with age affecting about a third of patients over 40 and is particularly likely if there is facial infection. The pain may be continuous and burning with increased sensitivity in the affected areas, or a spasmodic shooting type, or, rarely, of an itchy, crawling variety. The overlying skin is numb or exquisitely sensitive to touch.

Treatment of active herpes zoster may include:

Post-herpetic neuralgia may be difficult to treat successfully. It may respond to tricyclic antidepressant medications such as amitriptyline or anti-epileptic medication such as carbamazepine or sodium valproate.

The incidence of herpes zoster is reduced by vaccination, which is recommended for adults over 50 years and people who are immune suppressed

Less common localised viral skin infections

Less common viral skin infections due to the parapox virus include:

Milker’s nodules.

Orf.