Infectious rashes in childhood

Infectious rashes are common in children and are caused by viruses, bacteria, fungi, or parasites. In acutely ill patients, perform initial management of rash to identify red flags for a life-threatening rash. A detailed history and skin examination are essential in all patients, as infectious rashes can often be diagnosed clinically. Diagnostic testing may be obtained to confirm certain diagnoses (e.g., measles, rubella, bacterial or fungal infections) and to exclude alternative diagnoses in case of diagnostic uncertainty. Management is based on the underlying cause. Most viral infections are managed with supportive care. Pharmacological treatment with antibiotics, antivirals, or ectoparasiticides may be indicated depending on the causative organism.

For information on rashes associated with congenital infections, see “Congenital TORCH infections.” For more information on each specific infection, see the respective articles.

Viral ^[1][2][3]

• Chickenpox
• Hand, foot, and mouth disease ^[4]
• Measles
• Erythema infectiosum (Fifth disease)
• Roseola infantum
• Rubella
• Molluscum contagiosum
• Herpes simplex virus infections ^[5]
• Shingles
• Gianotti-Crosti syndrome
• Dengue
• Zika virus
• Chikungunya virus
• Acute HIV exanthem ^[6]
• Nonspecific viral exanthems ^[6]

Bacterial ^[1][6]

• Scarlet fever
• Skin and soft tissue infections, e.g.:
  • Impetigo ^[2]
  • Staphylococcal scalded skin syndrome
  • Folliculitis
• Meningococcal septicemia
• Lyme disease
• Rocky Mountain spotted fever (RMSF)
• Toxic shock syndrome
• Disseminated gonococcal infection ^[3]

Fungal ^[1]

• Dermatophyte infections
• Candidiasis
• Pityriasis versicolor

Parasitic ^[1]

• Scabies
• Lice

Focused history ^[2][6]

• Rash characteristics
  • Onset, duration, progression
  • Distribution
• Associated symptoms
  • Constitutional symptoms (e.g., fever)
  • Pruritus
  • Arthralgias
  • Pharyngitis
• Exposures
  • New medications or products
  • Recent travel
  • Sick contacts
  • Arthropod bites

Focused examination ^[2][6]

• Vital signs: to assess for fever
• General appearance: to assess for irritability or lethargy
• Lymph node examination
• Skin examination: See “Primary skin lesions” and “Secondary skin lesions” for describing and documenting rashes.
  • Determine lesion morphology (e.g., macules, papules, vesicles, pustules).
  • Examine the entire skin and mucosa to determine rash distribution.
  • Describe additional lesion characteristics (e.g., color, presence of scale or Nikolsky sign, blanchable).

Approach ^[1][2][6]

• Acute illness: Perform initial management of rash, including identifying red flags for a life-threatening rash.
• Ensure appropriate isolation precautions (e.g., for suspected measles or meningococcal septicemia).
• In children, diagnosis is usually clinical.
• Obtain laboratory studies as needed to:
  • Identify pathogen for diagnostic confirmation
  • Exclude alternative diagnoses (see “Mimics”)
• Consider biopsy to rule out mimics in case of diagnostic uncertainty.

Laboratory studies ^[1][6]

• CBC: to identify leukocytosis, thrombocytopenia
• Microbiological studies: to identify causative organism based on clinical suspicion
  • Diagnostics for scarlet fever (e.g., rapid strep test, throat culture)
  • Diagnostics for measles (e.g., measles-specific antibodies, RT-PCR)
  • Diagnostics for rubella (e.g., rubella-specific antibodies, RT-PCR)
  • Diagnostics for dermatophyte infections (e.g., KOH test, fungal culture)
  • Diagnostics for HSV infections (e.g., PCR, viral culture)
  • Diagnostics for RMSF (e.g., Rickettsia antibody panels)
  • Diagnostics for Lyme disease (e.g., Lyme antibody testing)
  • Diagnostics for meningitis in children (e.g., blood and CSF cultures)

Common causes of infectious rash in children [1][2][7][8]
Disease (pathogen)	Characteristic clinical features		Management
Measles (Measles virus)		Prodrome Coryza, cough, and conjunctivitis Koplik spots Fever Erythematous, blanching rash with macules and papules Begins on the face, frequently behind the ears Spreads to the rest of the body Possible desquamation	Airborne precautions Serology or PCR to confirm the diagnosis Supportive care Vitamin A supplementation in selected patients See “Management of measles.”
Scarlet fever (Streptococcus pyogenes)		Prodrome of fever, tonsillopharyngitis Fine, erythematous blanching rash with macules and papules (sandpaper-like texture) Begins on the neck or trunk and spreads rapidly across the body [9] Desquamation 7–10 days after rash resolves Strawberry tongue Pastia lines Flushed cheeks, perioral pallor	Rapid strep test or throat culture to confirm the diagnosis Antibiotics for GAS pharyngitis See “Treatment of scarlet fever.”
Rubella (Rubella virus)		Prodrome Mild nonspecific symptoms, low-grade fever Suboccipital and postauricular lymphadenopathy Forchheimer sign Fine, erythematous rash with macules and papules Begins behind the ears and spreads to the trunk and extremities Nonconfluent, medium-sized spots	Droplet precautions Serology or PCR to confirm the diagnosis See “Management of rubella.”
Fifth disease (erythema infectiosum) (Parvovirus B19)		Prodrome of systemic symptoms, arthralgias Initial slapped cheek appearance Rash on trunk and extremities Macules and papules that become confluent (lace-like, reticular appearance) May recur with environmental changes (e.g., sunlight, heat exposure) over weeks to months	Clinical diagnosis Supportive management See “Management of parvovirus B19 infection.”
Roseola infantum (exanthem subitum) (Human herpesvirus 6)		Prodrome Sudden high fever for 3–7 days Nagayama spots Patchy, blanching rose-pink rash with macules and papules Develops as fever subsides Originates on the trunk	Clinical diagnosis Supportive care Management of complications (e.g., febrile seizures) See “Treatment of roseola infantum.”
Chickenpox (varicella) (Varicella zoster virus)		Starry sky: simultaneous occurrence of various stages of rash (e.g., pruritic vesicles on erythematous base, crusted pustules) Starts centrally (trunk, face) and spreads to extremities Mucous membrane involvement (typically oropharyngeal)	Clinical diagnosis Supportive care Antiviral therapy for VZV infection in selected patients See “Treatment of chickenpox.”
Hand, foot, and mouth disease (Group A Coxsackievirus)		Painful oral ulcers Rash with macules and papules Becomes vesicular Affects feet and hands	Clinical diagnosis Supportive care
Impetigo [10] (Streptococcus pyogenes, Staphylococcus aureus)		Papules that evolve into vesicles and/or pustules Honey-colored crust Most common on the face and extremities Negative Nikolsky sign	Clinical diagnosis Antibiotics See “Treatment of impetigo.”

Measles and rubella are nationally notifiable diseases in the US. Notify the local health department of any suspected cases. ^[1]

Management depends on the specific cause.

• Most viral infections are managed with supportive care.
• Pharmacological treatment (e.g., antibiotics, antivirals, ectoparasiticides) may be indicated depending on the causative organism.

• Pityriasis rosea
• Dermatoses
  • Atopic dermatitis
  • Allergic contact dermatitis
  • Irritant contact dermatitis
  • Seborrheic dermatitis
• Drug hypersensitivity reactions
  • Exanthematous drug eruptions
  • Drug reaction with eosinophilia and systemic symptoms (DRESS syndrome)
  • Stevens-Johnson syndrome
  • Toxic epidermal necrolysis
  • Acute generalized exanthematous pustulosis
• Urticaria
• Rosacea
• Vasculitides
  • Kawasaki disease
  • IgA vasculitis
• Multisystem inflammatory syndrome in children
• Systemic lupus erythematosus

Always consider drug reactions as a potential cause of rash.