Scalp Cellulitis

Scalp cellulitis is bacterial infection of the scalp skin and subcutaneous tissue, usually Staphylococcus aureus or streptococci, entering through wounds, folliculitis, lice, eczema or surgery. The scalp's rich blood supply and emissary veins let infection spread to the skull and intracranial spaces.

• Risk factors: head trauma, scalp laceration, shaving, tinea capitis, diabetes, HIV, malnutrition, neonatal scalp electrodes.

Painful, red, warm, boggy swelling of the scalp with hair loss, pus at follicles, fever and tender occipital or cervical nodes.

• Differential diagnosis: kerion (inflammatory tinea capitis), folliculitis decalvans, dissecting cellulitis of the scalp, subgaleal abscess, skull osteomyelitis, scalp haematoma, herpes zoster, pediculosis with impetigo, Pott puffy tumour, scalp tuberculosis.
• Complications: subgaleal abscess, osteomyelitis of the skull, subdural empyema, meningitis, brain abscess, sepsis, scarring alopecia.

Clinical, with fungal exclusion.

• KOH and fungal culture of hair and scale; bacterial swab; full blood count, CRP, blood cultures if febrile.
• CT head with contrast if skull penetration, deep swelling or neurological signs; ultrasound for subgaleal collections.
• Glucose and HIV test.

Antibiotics and drainage of any collection.

• Supportive: warm compresses, wash with chlorhexidine 4 percent, analgesia, avoid shaving, hygiene, tetanus toxoid if due.
• Pharmacological: flucloxacillin 500 mg to 1 g four times daily for 7 to 10 days (children 12.5 to 25 mg/kg four times daily); clindamycin 300 to 450 mg three times daily if penicillin allergic or MRSA; severe or deep infection: ceftriaxone 2 g IV daily with metronidazole 500 mg IV every 8 hours, plus vancomycin 15 to 20 mg/kg IV every 12 hours. If kerion: oral antifungal (terbinafine 250 mg daily for 4 weeks, children by weight; griseofulvin 20 mg/kg daily for 6 to 8 weeks) and no antibiotics unless bacterial infection.
• Procedures: incision and drainage of subgaleal abscess; debridement of infected bone; neurosurgical drainage for intracranial extension.
• Special groups: pregnancy, flucloxacillin or cefalexin; neonates, admit for IV antibiotics; diabetes, tight glucose control; HIV, culture for resistant organisms.
• Red flags: headache, vomiting, fever with drowsiness, forehead swelling, seizures, boggy fluctuant swelling, bone exposure.
• Follow-up: review at 48 hours; imaging for non response; trichology or dermatology for scarring.