How can I differentiate between a simple abscess and a more complicated skin infection that may require referral?

A simple abscess typically presents with localised signs of infection such as heat, redness, pain, and swelling NICE NG125. However, a skin infection or abscess may be considered more complicated and require referral if it presents with additional features or specific characteristics.

• Systemic signs of infection: The presence of fever or a raised white blood cell count, in addition to local signs, indicates a more serious infection NICE NG125.
• Cellulitis: If cellulitis is present, it suggests a spreading infection that requires antibiotic treatment NICE NG125.
• Size: While specifically mentioned for diverticular abscesses, abscesses greater than 3 cm may require interventions such as percutaneous drainage or surgery NICE NG147. This principle can be extended to large cutaneous abscesses.
• Lack of clinical improvement or deterioration: If an abscess does not improve clinically or deteriorates despite initial management, further assessment or re-imaging may be necessary NICE NG147.
• Specific severe skin conditions: Conditions like acne fulminans require urgent same-day referral to an on-call hospital dermatology team NICE NG198. Acne conglobata or nodulo-cystic acne also warrant referral to a consultant dermatologist-led team NICE NG198.
• Diagnostic uncertainty: If there is uncertainty about the diagnosis of the skin condition, referral to a consultant dermatologist-led team is recommended NICE NG198.
• Failure of treatment: Moderate to severe acne that has not responded to previous treatment, particularly if it included an oral antibiotic, is a reason to consider referral NICE NG198. This principle can be applied to other skin infections failing to respond to appropriate treatment.
• Need for microbiological guidance: Samples of pus from a drained abscess should be sent to microbiology to tailor antibiotic treatment based on sensitivities NICE NG147.