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Referral and warning signs
When to refer
Refer if: Large carbuncle, Lesion on face (danger triangle), Signs of systemic illness/sepsis, Immunocompromised patient, Failure to resolve with initial management, Recurrent furunculosis (for investigation/decolonization).
Red flags
- Lesion within the facial 'danger triangle' (area from corners of mouth to bridge of nose).
- High fever / Systemic toxicity.
- Rapidly spreading redness/cellulitis.
- Neurological signs (if facial lesion - cavernous sinus thrombosis).
- Failure of fluctuant lesion to drain after I&D.
Signs and symptoms
- Furuncle: Starts as tender, red nodule around a hair follicle. Becomes painful, fluctuant (pus-filled), and may develop a central 'head' or point before spontaneously draining.
- Carbuncle: Larger, deeper, multi-headed lesion. Often on back of neck, shoulders, thighs. Associated with more systemic symptoms (fever, malaise).
Risk factors
- Staphylococcus aureus carrier state (nose, skin).
- Poor hygiene.
- Friction from clothing.
- Diabetes Mellitus.
- Immunosuppression (HIV, malnutrition).
- Obesity.
- Pre-existing skin conditions.
Diagnosis
Clinical assessment
Diagnosis based on clinical appearance of a tender, erythematous, fluctuant nodule or larger carbuncle.
Differential diagnosis
- Infected epidermal cyst.
- Hidradenitis suppurativa.
- Acne nodule/cyst.
- Cellulitis (more diffuse).
- Lymphadenitis.
Investigations
- Usually clinical diagnosis.
- Pus swab for Gram stain, Culture & Sensitivity (if drained, recurrent, or systemic antibiotics needed).
- Blood glucose check (if recurrent or diabetic risk factors).
- Consider HIV test if recurrent.
Diagnostic criteria
Clinical appearance of localized skin abscess related to hair follicle(s).
Management
Non-pharmacological management
- Warm Compresses: Apply frequently to encourage localization and spontaneous drainage. (LOC: HC2)
- Incision and Drainage (I&D): Definitive treatment once lesion is fluctuant. Perform under aseptic conditions, make incision over most fluctuant point, allow pus to drain, may need gentle exploration/breaking of loculations, consider packing cavity loosely with gauze wick (especially carbuncles) to allow continued drainage. (LOC: HC2/3)
- Maintain good hygiene.
Pharmacological treatment
- Antibiotics: Not always needed for simple, small furuncles drained effectively. Indications for antibiotics: Large size (carbuncle), Surrounding cellulitis, Location on face (risk of cavernous sinus thrombosis), Systemic symptoms (fever), Immunocompromised host, Recurrent infections.
- - Choice (Cover Staph aureus): Cloxacillin 250-500 mg PO QID (before food) for 5-7 days. (Child: 12.5-25 mg/kg/dose). (LOC: HC2)
- - Alternative (Penicillin Allergy): Erythromycin 500 mg PO QID. (Child: 7.5-12.5 mg/kg/dose). (LOC: HC2)
- - Clindamycin or TMP-SMX may be considered if MRSA suspected.
- Analgesia: Paracetamol or NSAIDs.
Monitoring
Monitor for resolution after drainage/antibiotics. Ensure packing removed appropriately (if used). Watch for signs of spreading infection.
Complications
- Cellulitis.
- Sepsis (rare).
- Cavernous sinus thrombosis (if facial 'danger triangle' lesion).
- Scarring.
- Recurrence.
Prevention
- Good personal hygiene, use of antiseptic soaps.
- Treating underlying conditions (diabetes).
- Consider decolonization therapy (e.g., mupirocin nasal ointment, antiseptic washes) for recurrent infections (specialist advice).
Patient education
- Explanation of boil/carbuncle.
- Importance of warm compresses.
- Need for I&D if fluctuant.
- How to care for wound after drainage.
- Importance of completing antibiotics if prescribed.
- Hygiene measures to prevent recurrence/spread.
- Avoid squeezing lesions.
Uganda-specific notes
Common skin infections. I&D is key treatment for fluctuant lesions. Cloxacillin is standard antibiotic choice. Consider underlying HIV/diabetes in recurrent cases.
References
- Uganda Clinical Guidelines (UCG) 2023
Chapter 22, Section 22.1.2