Skin Abscess and Folliculitis

Essentials

• Minor skin abscesses (boils) can be treated by incision and drainage without the need for systemic antimicrobials.
• Recurrent abscesses (furunculosis) call for the identification of predisposing factors, improvement of personal hygiene and, if necessary, topical treatment of nasal staphylococcal colonisation.

Aetiology and terminology

• The most common causative agent is Staphylococcus aureus.
• If the inflammation is limited to the hair follicle the condition is called folliculitis (pictures 1 2).
• If the inflammation spreads to the surrounding tissues the condition is referred to as an abscess (a furuncle, pictures 3 4).
• An abscess may spread further via cutaneous interconnecting channels to form an aggregate of furuncles, i.e. a carbuncle.
• Sycosis barbae (barber's itch) is deep folliculitis of the beard region (pictures 5 6).

Diagnosis

• Diagnosis is based on clinical presentation.
• Often seen on the face and hairy skin areas, scalp, groins, thighs and axillae.
• Folliculitis manifests as a yellowish pustule of 1-3 mm diameter with surrounding erythema.
• An abscess is a hot, red and painful lump under the skin, which may exude purulent material when “ripe”.

Investigations

• Bacterial culture is only indicated in complicated or prolonged cases.
• In the case of poor treatment response, the possibility of MRSA Multidrug-Resistant Bacteria in Hospitals should be kept in mind, especially if there is preceding history of travel or hospital care abroad.
• Fungal samples (for microbiology and culture) whenever tinea is suspected.

Differential diagnosis

• The most important differential diagnoses are the early stages of erysipelas, cellulitis and necrotising infections.
• Keep in mind the possibility of secondary cellulitis if the patient has general symptoms or if the erythema extends widely outside the abscess area.
• It is important to identify causes other than infectious ones.
  • Acne, acneiform drug eruptions, rosacea
  • Oily skin creams, occupational provoking factors (e.g. oils and halogenated hydrocarbons), skin occlusion (e.g. plasters), friction, sweating and maceration, hair removal with a razor blade.
  • In individuals with more pigmented skin types, pseudofolliculitis of the beard area (pseudofolliculitis barbae) and neck (acne cheloidalis nuchae).
• The following pathogens may also cause a clinical picture that resembles folliculitis:
  • tinea (particularly around the beard area and scalp)
  • herpes and Herpes varicella-zoster (may cause grouped pustules)
  • gram-negative bacteria, such as Pseudomonas aeruginosa (for example, from dirty jacuzzi pools or following a long course of antimicrobials) or Malassezia yeast (on the back or chest).

Treatment

• The treatment of folliculitis is usually topical.
• On hairy skin areas (e.g. thighs) superficial folliculitis is a physiological phenomenon that doesn't always need treatment.
• The affected areas should be washed with soap or a low pH skin cleanser.
• If necessary, antimicrobial creams (e.g. fusidic acid) or antiseptic preparations (e.g. chlorhexidine or benzoyl peroxide) may be used.

Furunculosis

• Recurrent occurrence of furuncles
• Aetiology is unknown, but hereditary factors, diabetes, immunosuppression (picture 8) and undernourishment all predispose the person to furunculosis.
• Furunculosis may begin after a journey abroad (particularly in countries with warm climate) Skin Problems in Returning Travellers.
• Cases refractory to treatment
  • Bacterial culture is indicated since MRSA may be the cause of recurrent furuncles.
  • Additionally, it is a good idea to ask the laboratory to determine PVL (Panton-Valentine leukocidin), i.e. an exotoxin specific to S. aureus bacteria. Both methicillin-sensitive (MSSA) and methicillin-resistant (MRSA) S. aureus may produce it.
• It is important to differentiate furunculosis from acne (e.g. acne conglobata Acne) and hidradenitis suppurativa (deep furuncular lesions in flexural sites).
• The following measures are recommended in furunculosis: improved personal hygiene, antiseptic cleansing lotions (e.g. chlorhexidine or benzoyl peroxide) or antimicrobial creams, daily changing of bed linen, towels and clothing.
• Predisposing factors should be investigated.
• Moreover, the eradication of nasal S. aureus colonisation may be attempted with antibacterial creams, e.g. mupirocin cream twice daily for 5 days or fusidic acid cream for 1-2 weeks.
• As an addition to the topical treatment in severe cases (> 3 recurrences/6 months), clindamycin 150 mg 1-2 times daily for 1-3 months may be given as prophylactic treatment. Antimicrobials from the tetracycline, sulpha and macrolide groups have also been used.

Consultation

• Emergency treatment in a hospital and, if indicated, surgery is recommended in complicated abscesses, severe skin infections and septic conditions.
• In furunculosis refractory to treatment, a specialist in dermatology or infectious diseases should be consulted (verification of diagnosis, implementation of more effective eradication treatment).

Pictures