Furunculosis (Boils)

Patients typically report that the lesion started as a small, painful pimple that enlarged rapidly over several days. They describe:

• • Increasing pain, swelling, and a feeling of pressure or throbbing centered on a specific spot.

  • The boil may eventually drain spontaneously, releasing pus.

  • Systemic symptoms such as fever, fatigue, or generalized malaise may be present, particularly with larger or multiple lesions (carbuncles).

Risk Factors: Patients may report factors that compromise the skin barrier or indicate Staphylococcus colonization:

• • Staph carrier state (e.g., recurrent infections, nose/groin colonization).

  • Underlying conditions like diabetes, obesity, or immunosuppression.

  • Skin trauma from eczema, scratching, shaving, or friction (e.g., tight clothing).

  • Environmental factors such as crowding, poor hygiene, or high heat/humidity.

Crucial Note for Darker Skin Tones: 

Patients may not describe a visible "redness" (erythema). Instead, they may report feeling an itchy, tender, hard lump or notice a dark, purple, or brown discolouration that is warm to the touch. They should be warned that post-inflammatory hyperpigmentation (PIH) is extremely common after the boil heals.

The primary finding is a tender, firm, warm nodule centered around a hair follicle. It may have a central area of "pointing," where yellow/white pus is visible beneath the surface.

Appearance by Skin Tone:

• Lighter Skin: The nodule is typically erythematous (red) and inflamed.

• Darker Skin Tones: The lesion is often violaceous, purple, or brown in hue. Rely on warmth, tenderness, and induration (firmness) rather than visible redness for diagnosis.

• Common Locations: Areas prone to friction, sweating, or hair: buttocks, groin, axillae, neck, face, and posterior thighs. Surrounding cellulitis or regional lymphadenopathy (swollen nodes) may be present. A carbuncle is a cluster of coalescing boils.

Investigations (When Needed):

Swab: Send pus for Culture and Sensitivity (C&S) before starting antibiotics, especially for severe, recurrent, or suspected MRSA cases.

Bloodwork: Check HbA1c or fasting glucose if diabetes is suspected.

Management focuses on drainage, antibiotics for systemic cases, and preventing recurrence.

1. Local Measures / Self-care:

• Apply warm compresses for 20 minutes, 3–4 times per day, to encourage drainage.

• Instruct the patient not to squeeze or pop the boil themselves to prevent forcing bacteria deeper into the tissue.

• Once draining, keep the area clean with antibacterial soap and cover it with a loose dressing.

2. Medical Treatment (Incision & Drainage - I&D):

• I&D is the definitive treatment for most furuncles and all carbuncles once the boil has "pointed" or fluctuated.

• The procedure involves local anaesthesia, incision, draining the pus, breaking up loculations, and packing the cavity with gauze for 24–48 hours. Always send pus for culture.

3. Antibiotics: Indicated for: systemic symptoms (fever), multiple or widespread lesions, surrounding cellulitis, or if the patient is immune-compromised.

• First-line (MSSA): Flucloxacillin or Cephalexin.

• MRSA Suspected/Confirmed: Clindamycin, Doxycycline/Minocycline, or Trimethoprim-sulfamethoxazole (TMP-SMX).

4. Decolonisation Protocol (Recurrent Cases): This protocol targets the Staph reservoir:

• Topical Mupirocin: Applied to the nares (nostrils) twice daily for 7–14 days.

• Antiseptic Wash: Daily use of a body wash containing Benzoyl Peroxide (4–10%) or Chlorhexidine for 1 week, followed by 2–3 times per week maintenance.

• Hygiene: Daily laundering of towels and linens; avoid sharing personal items.

Special Considerations in Darker Skin Tones:

Diagnosis: Rely heavily on warmth, induration, and pain over redness. Misdiagnosis as hyperpigmentation or cystic acne is possible due to the violaceous or brown hue.

Complications: Patients have a higher risk of developing Post-inflammatory Hyperpigmentation (PIH) and Keloid or Hypertrophic Scarring (especially on the chest, back, and shoulders). Advise sun protection and gentle skin care to minimize PIH.

NCBI Bookshelf – Carbuncle / Furuncle (StatPearls): https://www.ncbi.nlm.nih.gov/books/NBK554459/

DermNet NZ – Boils / Furuncles: https://dermnetnz.org/topics/boil

DermNet NZ – Folliculitis and Furunculosis (CME module): https://dermnetnz.org/cme/bacterial-infections/folliculitis-and-furunculosis