Exanthem is the medical term for a widespread rash typically accompanied by systemic symptoms such as fever, malaise, and headache. These rashes are most common in childhood and usually result from viral infections, representing a reaction to a toxin, direct skin damage by the organism, or an immune response.
What are exanthems?
Exanthems, or reactive rashes, appear as spots or blotches that may be itchy or non-itchy. They are often more prominent on the trunk than extremities. Preceding symptoms include feeling unwell with fever, headache, cough, sore throat, nausea, vomiting, diarrhoea, or abdominal pain. Viral exanthems frequently occur in small epidemics among children.
Who gets exanthems?
Exanthems predominantly affect children, though they can occur at any age. They are very common during childhood, often linked to seasonal viruses like respiratory or enteroviruses in winter and summer.
What causes exanthems?
Most exanthems stem from viral infections. They are classified as specific viral exanthems with distinctive rashes and prodromes, or non-specific viral exanthems without unique features.
Specific viral exanthems
These have known causative viruses and characteristic patterns:
- Chickenpox (varicella): Primary varicella-zoster virus infection causes pruritic papules, vesicles, pustules, and crusts mainly on the face and trunk. Scarring occurs from deep lesions.
- Measles (morbilli): Prodrome of fever, malaise, anorexia, conjunctivitis, cough, coryza. Koplik spots (oral papules) precede the morbilliform exanthem starting on cheeks, spreading to trunk and limbs.
- Rubella: Mild fever, lymphadenopathy, then fine maculopapular rash starting on face.
- Roseola infantum (exanthem subitum): High fever followed by pink macules/papules on trunk.
- Fifth disease (erythema infectiosum): Parvovirus B19 causes slapped-cheek rash and lacy extremities.
- Hand foot and mouth disease: Coxsackievirus leads to oral ulcers and vesicular rash on hands/feet.
Bacterial exanthems
- Scarlet fever (streptococcal toxin)
- Staphylococcal scalded skin syndrome
- Toxic shock syndrome
- Secondary syphilis
- Meningococcaemia
- Rickettsial infections
Other infectious causes
- Infectious mononucleosis (Epstein-Barr virus)
- Hepatitis B
- COVID-19
Drug-induced exanthems
Common with antibiotics and NSAIDs, mimicking viral patterns like morbilliform or pityriasis rosea-like rashes.
Acute connective tissue diseases
- Dermatomyositis
- Still disease
Unknown cause
Kawasaki disease: Fever, rash, conjunctivitis, strawberry tongue, peeling; affects coronary arteries.
Non-specific viral exanthems
These lack distinctive features and are linked to common viruses like enteroviruses. No treatment needed; resolves spontaneously. Symptomatic relief with paracetamol, antihistamines, emollients.
Pityriasis rosea
Affects teens/young adults. Herald patch (oval, scaly) precedes fir-tree patterned plaques on trunk. Resolves in 6-12 weeks. Treat itch with mild topical steroids or UVB.
Gianotti-Crosti syndrome
Papular rash in children 6 months-12 years, lasts 2-8 weeks. Starts on thighs/buttocks, spreads to arms/face. Viruses: EBV, hepatitis B, coxsackievirus. Asymmetrical, mildly itchy.
Laterothoracic exanthem (APEC)
Affects young children (mostly girls), starts in axilla/groin, unilateral, spreads outward up to 12 weeks. Itchy plaques, possible viral prodrome.
Kawasaki disease (detailed)
Perioral/genital rash, swollen/peeling extremities, fever, lymphadenopathy, vasculitis especially coronary.
Clinical features distinguishing specific exanthems
| Exanthem | Prodrome | Rash Description | Distribution |
|---|---|---|---|
| Chickenpox | Mild fever, malaise | Papules → vesicles → crusts | Face, trunk |
| Measles | Fever, cough, Koplik spots | Morbilliform macules | Face → trunk/limbs |
| Roseola | High fever then defervescence | Pink macules/papules | Trunk → neck/extremities |
| Fifth disease | Mild URI | Slapped cheeks, lacy | Face, extremities |
| Hand-foot-mouth | Fever, sore throat | Vesicles, oral ulcers | Hands, feet, mouth |
Diagnosis
Many exanthems are diagnosed clinically by pattern recognition. Test if sick patient, pregnancy exposure, or immunosuppression.
- Serology for specific viruses
- PCR from swabs/lesions
- Throat swab, blood cultures
- Full blood count, CRP, liver enzymes
- Skin biopsy if needed
Treatment
Tailored to cause. Symptomatic:
- Paracetamol/ibuprofen for fever
- Topical steroids/antihistamines for itch
- Emollients
- Antivirals/aciclovir for severe varicella/measles in at-risk
Vaccines prevent measles, rubella, varicella.
What is the differential diagnosis for exanthems?
- Drug eruptions
- Other viral infections
- Bacterial toxin-mediated (scarlet fever)
- Kawasaki
- Juvenile idiopathic arthritis
Frequently Asked Questions
Are exanthems contagious?
Yes, most viral exanthems are contagious via respiratory droplets or contact. Isolate until rash crusts (e.g., chickenpox).
How long do exanthems last?
Typically 3-14 days; non-specific resolve faster, pityriasis rosea up to 12 weeks.
When to see a doctor for a rash with fever?
Seek care if high fever >3 days, lethargy, breathing issues, rash non-blanching, or spreads rapidly.
Can exanthems scar?
Yes, chickenpox or severe cases with vesicles can scar.
Are antibiotics needed for viral exanthems?
No, they are viral; antibiotics only for bacterial complications.
References
- Viral skin infections. Nonspecific viral exanthems — DermNet NZ. 2009 (updated). https://dermnetnz.org/cme/viral-infections/nonspecific-viral-exanthems
- Viral skin infections. Specific viral exanthems — DermNet NZ. 2009 (updated). https://dermnetnz.org/cme/viral-infections/specific-viral-exanthems
- Exanthems (reactive rashes) — DermNet NZ. Author: Dr Amanda Oakley. Updated 2015-09. https://dermnetnz.org/topics/exanthems
- Childhood Rashes — TeachMePaediatrics. Recent access 2026. https://teachmepaediatrics.com/dermatology/dermatology/childhood-rashes/
- Viral Exanthem Rash: Symptoms, Causes & Treatment — Cleveland Clinic. Recent. https://my.clevelandclinic.org/health/diseases/22510-viral-exanthem-rash
