Chickenpox (varicella)

chickenpox · varicella · VZV

Usually mild in a healthy child, and dangerous in the neonate, the immunosuppressed, the pregnant and the adult.

GPBand B

Red flags

Any area of skin that becomes painful, hot, swollen or discoloured - invasive group A streptococcal infection, including necrotising fasciitis, is a recognised and lethal complication of chickenpox
A neonate, an immunosuppressed patient, or a pregnant woman - all need urgent specialist discussion and consideration of aciclovir or immunoglobulin
An adult or adolescent - substantially higher risk of varicella pneumonia, especially in smokers and in pregnancy
Breathlessness or cough - varicella pneumonia
Drowsiness, unsteadiness or seizures - cerebellitis or encephalitis
Dehydration from painful oral lesions

Recognise

On light skin

Crops of itchy red macules becoming papules then thin-walled 'dewdrop' vesicles on a red base, pustulating and crusting, all stages coexisting.

On brown and black skin

The red base around each vesicle is frequently not visible, so the eruption appears as scattered skin-coloured or grey vesicles and darker crusted papules against unremarkable skin, and it can look far less impressive than it is. The coexistence of lesions at different stages is the diagnostic feature and is entirely tone-independent - look for macules, vesicles and crusts side by side. Chickenpox in brown and black skin much more often leaves prolonged post-inflammatory hypopigmentation or hyperpigmentation, sometimes for many months, and families should be warned about this specifically, since it is distressing and frequently mistaken for scarring.

In any skin tone

Lesions at several different stages at the same time - the single most useful sign
Intensely itchy, centrally distributed, and involving the scalp
Mild fever and malaise, typically a well child
New crops for three to five days; no longer infectious once all lesions have crusted
Ask about pregnant, immunosuppressed and neonatal contacts

Distribution

Starts on the face, scalp and trunk and spreads centrifugally, with lesions concentrated centrally rather than on the limbs. Lesions at all stages - macule, papule, vesicle, pustule, crust - are present at once.

Photographs

Chickenpox on brown skin, at the crusted stage. Almost nothing here looks like the textbook 'dewdrop on a rose petal'. There is no visible e — Chickenpox on brown skin, at the crusted stage. **Almost nothing here looks like the textbook 'dewdrop on a rose petal'.** There is no visible erythematous base at all: the lesions read as dark, flat, hyperpigmented spots and small crusts scattered over the shins and feet. Lesions at different stages together is still the diagnostic feature, but on darker skin you are reading differences in texture and pigment, not in redness. Run a hand over the skin and use good light.
Fitzpatrick V (Fitzpatrick type estimated from the photograph, not stated by the source) · Biswarup Ganguly · Wikimedia Commons - Varicella zoster Infection - Howrah 2014-04-06 9765.JPG · CC BY 3.0

Provenance for every photograph in this library: image licences. How much of the corpus still has no darker-skin photograph: skin tone coverage.

Mimics

Hand, foot and mouth disease — Concentrated on hands, feet and mouth with oval lesions, rather than a centrally distributed crop at mixed stages
Eczema herpeticum — In a child with eczema, monomorphic punched-out erosions on eczematous skin point to herpes simplex, not varicella
Impetigo — Bullous impetigo can resemble a localised crop, but lacks the widespread mixed-stage distribution
Staphylococcal scalded skin syndrome — Both blister in children; SSSS shears, spares mucosa and has perioral radial fissuring

What to do in the ED

Identify who this patient is: healthy child, adult, pregnant, immunosuppressed, or neonate. That question, not the rash, determines management
Examine every lesion site for secondary bacterial infection and specifically for disproportionate pain, which is the earliest sign of invasive group A streptococcal disease
Aciclovir is not routine in an otherwise healthy child. CKS suggests considering oral aciclovir for an immunocompetent, non-pregnant adolescent aged 14 or older, or adult, presenting within 24 hours of rash onset - not for younger children. Discuss urgently in pregnancy, immunosuppression and the neonate
Identify pregnant and immunosuppressed contacts; post-exposure prophylaxis is time-critical
Symptomatic treatment: paracetamol rather than ibuprofen, because non-steroidal use in chickenpox is associated with severe skin and soft tissue infection; oral antihistamine and emollient for itch
Exclusion advice: the two UK sources differ and you should give both. UKHSA's education guidance says stay away from the setting until 5 days after the rash first appears; NICE CKS says until all vesicles have crusted over. CKS reconciles them by noting infectivity continues until lesions are dry and crusted, usually about 5 days after rash onset. In practice, advise 5 days as the minimum and until crusting if that takes longer
Warn explicitly about the pigment changes that follow in darker skin, which are not scarring

Disposition

Supportive care at home for a healthy child. Urgent specialist discussion for neonates, pregnancy, immunosuppression, and for any complication; admit for invasive infection, pneumonia or neurological features.

Safety-netting

Use paracetamol rather than ibuprofen. Return immediately if any patch of skin becomes painful, red, hot or swollen, if the child is in severe pain anywhere, if they become drowsy, unsteady or confused, if breathing becomes difficult, or if a high fever returns after the spots have started crusting. Stay away from school, and from anyone pregnant, any newborn and anyone with a weak immune system, for at least 5 days after the spots first appeared and until every spot has crusted over - whichever is longer. UK guidance is worded both ways and this covers both.

Sources

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