Etiology and Pathology
Furuncles and carbuncles are acute bacterial purulent inflammations of hair follicles and surrounding tissues, most commonly caused by Staphylococcus aureus, though Staphylococcus epidermidis or other pathogenic bacteria may also be involved.
Furuncles involve a single hair follicle and its surrounding tissues and are associated with factors such as poor local skin hygiene, abrasions, blocked secretions of hair follicles and sebaceous glands, or reduced systemic immunity. Staphylococcus aureus often produces coagulase, which converts fibrinogen into fibrin in the infected area, restricting bacterial spread. Consequently, the inflammation is usually localized with the formation of a purulent core.
Carbuncles involve the simultaneous inflammation of multiple adjacent hair follicles and surrounding tissues or result from the fusion of several furuncles. The inflammation typically begins at the base of the hair follicles and spreads through the less resistant subcutaneous tissue, expanding along the superficial layer of the deep fascia. This creates multiple purulent foci involving clusters of hair follicles. Carbuncles can extend to the deep subcutaneous connective tissue, causing impaired blood circulation and necrosis of the overlying skin. Spontaneous rupture is often slow, systemic reactions are more severe, and in some cases, sepsis may occur.
Clinical Presentation
Furuncles frequently occur on the scalp, face, neck, and back. Initially, a localized hard nodule (less than 2 cm in diameter) with redness, swelling, and pain appears on the skin's surface. The inflammation later enlarges, and the central tissue of the nodule undergoes necrosis and softening, forming a yellowish-white purulent core that is soft and fluctuant to the touch. Most purulent cores eventually detach and rupture spontaneously, with the discharge of pus followed by resolution of the inflammation and healing of the lesion. Some furuncles, known as "blind boils," lack a purulent core and require anti-inflammatory treatment. When multiple furuncles appear simultaneously or recur over a period of time, the condition is termed "furunculosis," which may be associated with reduced infectious resistance (e.g., in diabetes) or poor hygiene.
Carbuncles commonly affect the thick-skinned regions of the nape and back. Early manifestations include a localized area of skin induration, warmth, pain, and a dark red discoloration of the skin, with several raised bumps or pustules. Associated symptoms include fever, loss of appetite, and general malaise, though pain is often mild initially. As the lesion progresses, the area of induration enlarges with surrounding infiltrative edema, regional lymph node enlargement, worsening pain, and more pronounced systemic symptoms. Subsequently, multiple purulent points may merge and enlarge, with necrosis of central tissue leading to drainage of pus and formation of a honeycomb-like surface. Surrounding skin often has a purplish-brown discoloration, and spontaneous healing is difficult. Delay in management can result in worsening lesions and severe systemic reactions.
Furuncles and carbuncles of the maxillofacial region, especially those located in the "danger triangle" of the nose, upper lip, and surrounding areas, are particularly dangerous. Known as facial furuncles or labial carbuncles, these lesions present with more severe clinical symptoms. Improper handling, such as squeezing the lesion, can allow bacteria to travel through the angular vein or ophthalmic vein into the cranial cavernous sinus, causing intracranial suppurative cavernous sinus thrombophlebitis. This condition can lead to swelling of the face, chills, high fever, headache, vomiting, loss of consciousness, and even death.
Diagnosis and Differential Diagnosis
Carbuncles involve larger lesions and may feature multiple purulent cores. In addition to localized redness, swelling, and pain, systemic symptoms such as fever may also occur. Routine blood tests, blood glucose, urine glucose, and serum albumin levels should be assessed. For cases requiring antibiotics, bacterial culture and drug sensitivity tests of the pus should be performed. Differential diagnoses include infected sebaceous cysts or acne infections.
Prevention and Treatment
Maintaining skin hygiene is important, especially in hot and humid environments, where frequent bathing and changing of undergarments can reduce sweat accumulation. Timely management of furunculosis is essential to prevent the spread of infection. Protecting the skin of infants can reduce the likelihood of abrasions or epidermal injuries.
Local Management
During the initial stage of a furuncle with redness and swelling, therapies such as hot compresses, ultrashortwave diathermy, and infrared light therapy may be applied.
For furuncles with a visible purulent core or fluctuation, the core may be carefully removed with a needle tip. Squeezing the lesion is contraindicated. After draining, an iodine-soaked gauze strip can be applied until resolution of inflammation.
For carbuncles, early treatment may include wet compresses with 50% magnesium sulfate and physical therapies. When purulent points, purplish-brown skin, or spontaneous rupture with pus drainage are present, incisive drainage using "+" or "++" shaped incisions is necessary. The incision should extend slightly beyond the inflamed tissue into healthy tissue, reaching the base of the carbuncle. Purulent and necrotic tissue should be debrided, and the cavity filled with iodine-soaked gauze strips, with dry gauze applied externally. Postoperative care involves monitoring wound bleeding and replacing the dressing when necessary. Anti-inflammatory treatment is crucial, and once the infection is controlled, "regenerating powder" may promote granulation tissue growth and wound healing. For extensive lesions where skin coverage is challenging, skin grafting may be required after granulation tissue formation.
Figure 1 Incision and drainage of a carbuncle
(1) Cross-shaped incision.
(2) Incision length slightly exceeding the inflamed area, with depth reaching the fascia.
(3) Placement of gauze strips in the wound cavity to control bleeding.
Medication Management
Furuncles and carbuncles causing symptoms such as fever, headache, and systemic discomfort—especially facial and labial carbuncles, which may be accompanied by acute lymphadenitis or lymphangitis—can be treated with penicillin or cephalosporin-class antibiotics. Patients with a history of diabetes require insulin or glucose-lowering medications.