Chickenpox
Usually mild. Paracetamol, not ibuprofen. Watch for skin infection and pneumonia, and protect high-risk contacts.
A 4-year-old girl has had a fever and an itchy rash for 2 days: spots, blisters and crusts at the same time, mostly on her trunk and face, some in her mouth. Her mother has been giving ibuprofen. Yesterday her aunt, who is 6 months pregnant and has never had chickenpox, visited.
Today one patch on her thigh is red, hot, swollen and very painful, and she is more unwell with a fever of 39.8 °C.
What advice for the child, what has happened on her thigh, and who else needs action?
- Unwell, breathless, or very red spreading skinPneumonia, bacterial skin infection, necrotising fasciitis, toxic shock: admit.
- Pregnant, newborn or immunosuppressed contactCheck immunity, may need immunoglobulin or antivirals.
- Healthy childParacetamol, fluids, calamine or emollient for itch, short nails.
- No ibuprofen or other NSAIDsLinked to severe skin and soft tissue infections.
- AciclovirAdults, teenagers, smokers, pregnant women, immunosuppressed, newborns, severe disease.
- No aspirin in childrenReye's syndrome.
- IsolationUntil all spots have crusted (usually 5 days after the rash starts).
- Breathlessness or cough (varicella pneumonia)
- Spreading red, hot, painful skin
- Drowsiness, unsteadiness, fits (encephalitis, cerebellitis)
- Bleeding into spots or bruising
- Newborn, immunosuppressed child
- Fever returning after day 4, or very high fever
- Secondary bacterial infection (group A Strep, necrotising fasciitis, toxic shock)
- Varicella pneumonia (adults, smokers, pregnancy)
- Encephalitis or cerebellar ataxia
- Immunosuppressed child
- Pregnant contact
- Neonatal varicella
| Infectious | From 2 days before the rash until all spots crust |
| Incubation | 10–21 days |
| Aciclovir (adult or teenager) | 800 mg orally 5 times daily for 7 days, within 24 hours of rash if possible |
| Aciclovir (immunosuppressed, newborn, complications) | IV, weight-based |
| Paracetamol | 15 mg/kg every 4–6 hours (max 4 doses in 24 hours) |
| Pregnant contact | Check immunity, non-immune: antiviral (7–14 days after exposure) or VZIG per guidance |
| Exclusion | School or nursery until all spots crusted |
Check every dose against a current drug reference and your hospital protocol.
On this page
What is chickenpox?
A highly contagious infection with varicella-zoster virus, spread by droplets and contact with blister fluid. Most children have a mild illness for about a week. Adults, pregnant women, newborns and immunosuppressed people get much sicker. The virus then lies dormant and can return as shingles later in life.
Typical course
- Days −2 to 0Mild fever, tiredness; already infectious
- Day 1–4Crops of red spots become blisters then crusts; itchy; spots at different stages at once
- Day 5–7All spots crusted; no longer infectious
- Day 7–14Crusts fall off; may leave marks
- Spots appear in crops, so red spots, blisters and crusts are seen together.
- Often starts on the face, scalp and trunk; can be in the mouth and genitals.
Complications
| Complication | Who | Clues |
|---|---|---|
| Bacterial skin infection | Children | Spreading redness, swelling, pain, fever returning |
| Necrotising fasciitis and toxic shock | Children, especially with NSAIDs | Severe pain, rapid spread, shock |
| Pneumonia | Adults, smokers, pregnant women | Cough, breathlessness, low SpO₂ |
| Encephalitis and cerebellar ataxia | Children | Drowsiness, unsteady walking |
| Haemorrhagic chickenpox | Immunosuppressed | Bleeding into spots |
| Neonatal varicella | Mother infected around delivery | Severe, can be fatal |
| Congenital varicella | Infection in the first 20 weeks of pregnancy | Scars, limb defects (rare) |
Who needs aciclovir?
- No antiviral
- symptom relief
Oral aciclovir within 24 hours of rash
- IV aciclovir
- admit
Exposed contacts
| Contact | Action |
|---|---|
| Pregnant woman | Ask about chickenpox history or check IgG. Non-immune: antiviral 7–14 days after exposure or VZIG per guidance; obstetric advice |
| Newborn (mother with chickenpox 7 days before to 7 days after delivery) | VZIG or IV aciclovir per neonatal team |
| Immunosuppressed (chemotherapy, high-dose steroids, HIV) | Check immunity; VZIG or antiviral per specialist |
| Healthy non-immune adult | Watch for symptoms; early aciclovir if rash appears |
Symptom care
- Paracetamol for fever and discomfort.
- No ibuprofen or other NSAIDs: linked to severe skin and soft tissue infections.
- No aspirin in children (Reye's syndrome).
- Calamine lotion, emollients, cool baths, loose cotton clothes, short nails.
- Sedating antihistamine at night for itch in children over 1 year.
- Plenty of fluids.
Treatment
Common mistakes
- Giving ibuprofen to a child with chickenpox.
- Missing necrotising fasciitis when fever returns with a painful red patch.
- Not asking about pregnant or immunosuppressed contacts.
- Not treating adults with aciclovir.
- Sending a child back to school before all spots crust.
Frequently asked questions
Why should ibuprofen be avoided in chickenpox?
NSAIDs are linked to severe bacterial skin infections such as necrotising fasciitis in chickenpox. Use paracetamol instead.
When can a child with chickenpox go back to school?
When all the spots have crusted over, usually about 5 days after the rash appeared.
Who needs treatment with aciclovir?
Adults, teenagers, smokers, pregnant women, people with lung disease or on steroids, newborns and immunosuppressed patients.
What should a pregnant woman do after contact with chickenpox?
Check whether she is immune. If not, she needs antiviral treatment or immunoglobulin per guidance, and obstetric advice.
Test yourself
Exam-style questions on this guide, from our two question banks. Choose an answer to see why each option is right or wrong.
1. Which pain reliever should be avoided in children with chickenpox?
Answer: Ibuprofen. NSAIDs are linked to severe bacterial skin infections in chickenpox.
- Paracetamol: Safe.
- Calamine lotion: Safe.
- Oral fluids: Safe.
- Chlorphenamine: Safe.
2. Who should receive aciclovir for chickenpox?
Answer: An adult smoker. Adults, teenagers, smokers, pregnant women after 20 weeks and immunosuppressed patients.
- Only children under 1 year: Not the criterion.
- Only if fever over 40 °C: Not the criterion.
- Every healthy child: Not needed.
- Nobody: Adults benefit.
3. When can a child with chickenpox return to school?
Answer: When all spots crust. Infectiousness ends when all lesions crust, usually about 5 days.
- When fever settles: Still infectious.
- After 2 days: Too early.
- After 3 weeks: Too late.
- Immediately: No.
4. A 20-week pregnant woman with no history of chickenpox had contact with a child with chickenpox 3 days ago. Varicella IgG is negative. What is offered?
Answer: Varicella immunoglobulin. Non-immune pregnant women exposed to varicella: VZIG within 10 days of exposure (or oral aciclovir from day 7–14 per some guidelines). If chickenpox develops: oral aciclovir within 24 h of rash (≥ 20 weeks), admit if pneumonia. Fetal varicella syndrome (< 20 weeks): limb hypoplasia, skin scarring, eye defects. Maternal infection 5 days before to 2 days after delivery → severe neonatal varicella → VZIG to baby.
- MMR vaccine today: MMR does not protect against varicella and is live.
- Varicella vaccine now: Varicella vaccine is live and contraindicated.
- Reassure, no action: There is a risk of maternal pneumonia.
5. A 30-year-old smoker develops chickenpox. On day 3 he is breathless with SpO₂ 89% and bilateral nodular shadows on chest X-ray. What is the management?
Answer: IV aciclovir. Varicella pneumonitis is commoner in adults, smokers, pregnant women and the immunosuppressed, usually 1–6 days after the rash. It needs admission, oxygen and IV aciclovir (10 mg/kg 8-hourly). Oral aciclovir within 24 hours of rash helps healthy adults and adolescents. Exposed non-immune pregnant women or immunocompromised people get varicella-zoster immunoglobulin (or aciclovir from day 7–14 after exposure). Avoid aspirin in children (Reye syndrome).
- Oral aciclovir at home: Pneumonitis needs IV therapy.
- Oral prednisolone: Steroids are not the treatment.
- Varicella vaccine now: The vaccine prevents disease; it does not treat it.
6. After chickenpox, where does varicella-zoster virus remain latent?
Answer: Sensory ganglia. VZV travels up sensory nerves and stays latent in dorsal root ganglia and cranial nerve ganglia (such as the trigeminal ganglion). When immunity falls (age, stress, immunosuppression), it reactivates as shingles in that dermatome. EBV is latent in B cells; CMV in monocytes and other cells.
- Skin epithelium: Active infection only.
- B lymphocytes: EBV latency.
- Bone marrow: Not the site.
- Salivary glands: CMV can persist here; not VZV.
7. Which immunoglobulin is most abundant in serum?
Answer: IgG. IgG makes up about 75% of serum immunoglobulin, crosses the placenta, opsonises and activates complement. IgA is the main antibody in secretions (the most produced overall). IgM is the first antibody in a response and is a pentamer. IgE mediates allergy and anti-parasite defence.
- IgA: Main secretory antibody.
- IgM: First made; pentamer.
- IgE: Lowest level; allergy.
- IgD: Low level; B-cell receptor.
References and dose sources
- NICE CKS — Chickenpox
- UKHSA — Varicella: the Green Book chapter 34
- Paracetamol dosing: Drugs.com: Acetaminophen (paracetamol) dosage (see also our paracetamol dose page)
- Aciclovir dosing: Drugs.com: Acyclovir (aciclovir) dosage (see also our aciclovir dose page)
- Chlorphenamine (chlorpheniramine) dosing: Drugs.com: Chlorpheniramine dosage (see also our chlorphenamine (chlorpheniramine) dose page)
- Flucloxacillin dosing: Drugs.com: Flucloxacillin (international) (see also our flucloxacillin dose page)
International guidance is linked where it reflects good practice. Where your hospital’s protocol differs, follow your hospital.