In most patients, clinical examination of the skin reveals a single erythematous papule, pustule or nodule that is tender and painful to touch. Adjacent redness of the skin may be present. Sometimes, more than one furuncle may develop in a relatively small area. Coalescence of several furuncles is called a carbuncle. Some of them may be draining pus, and they may also develop in several anatomic locations simulatenously. Closer inspection will reveal that furuncles develop at the center of the hair follicle, and constitutional symptoms, such as fever, malaise, and local lymphadenopathy occur only if the infection is severe.

As mentioned previously, furuncles can develop in any hair-bearing areas, but are most commonly found in the head and neck area, proximal extremities, including axilla, groins, and the gluteal region [9].

Diagnosis is primarily made during the clinical examination, and once the suspicion toward furunculosis is made, workup includes identification of the causative agent, which is done by performing cultures from swabs obtained at the site of infection. Additional laboratory investigations should include urine and blood glucose, as well as glycated hemoglobin (HBA1c) to identify possible diabetes mellitus as an underlying disease. If symptoms of other than localized skin infection are present, a complete blood count (CBC), as well as other laboratory tests should be performed to investigate possible systemic infection.

In patients with recurrent furunculosis, immunological investigations should be conducted, to exclude other possible underlying causes such as HIV, malignancies, or autoimmune diseases.

Apart from microbiological and laboratory tests, patient history and the rest of the physical examination might reveal details about the underlying cause, such as poor hygiene and increased perspiration which can be encountered among athletes, or the obese.

Treatment of furunculosis depends on the severity of infection, and can be either localized or systemic, but sometimes both therapies may be used. Sometimes, furuncles spontaneously burst and pus is drained onto the skin, but treatment is often necessary. particularly for larger lesions.

Localized therapy includes incision and draining of abscesses, using a scalpel blade. Application of heat and warm compresses provide consolidation of tissue and facilitate pus drainage. These methods are often sufficient in resolving this infection. However, in the presence of carbuncles, severe localized infection, or possible systemic infection, antibiotic therapy is necessary to eradicate the pathogen and resolve the infection.

When localized therapy does lead to cure, or if there is presence of single large furuncle (>5mm), oral antibiotic therapy is initiated. Systemic therapy is initiated if lesions do not resolve after initial antibiotic treatment, if there are signs of expanding infections, and if patients are immunosuppressed or at risk for endocarditis.

It is crucial to obtain swab cultures when antibiotic therapy is necessary, in order to get data regarding antimicrobial susceptibility, which is the key in choosing optimal antibiotic therapy [10]. However, due to the fact that these results often take at least a few days, empiric therapy is often initiated, and should be directed primarily against MRSA.

Guidelines suggest the use of double strength (DS) trimethoprim-sulfamethoxzole (TMP-SMX) 160/800mg po bid, clindamycin 300-450mg po tid, and doxycycline/minocycline 100mg po bid, for 5-10 days as empiric agents, with rifampicin 600mg po q24h being considered as adjunctive therapy [11]. If patients are at risk for endocarditis or systemic infection, treatment includes administration of vancomycin 15/20 mg/kg IV q8-12h, or daptomycin 6 mg/kg IV q24h [12].

For patients in whom the suggested treatment regimens did not resolve the infection, final resort includes the use of daptomycin in higher doses (8-12 mg/kg q24h), linezolid 600mg IV/po q12h, talavancin 10mg/kg IV q24h, or ceftaroline 600mg IV q8h.

Most cases of furunculosis resolve, with or without therapy, whether local therapy is used, or with administration of antibiotics. Usually, the most common complications of furunculosis are scarring and recurrence, but more severe infections may occur.

Recurrent furunculosis implies development of new furuncles despite all therapeutic measures, and certain individuals are not able to prevent the repeated occurrence of these lesions. This can be a troubling issue for patients, since boils in areas like the ear canal or nose can be very painful.

If several furuncles develop relatively close to each other, they can coalesce and form carbuncles, which are very large pus-draining lesions which increases the risk of developing a more severe infection of the skin, such as cellulitis, but also an infection that involves another site apart from the skin.

Furunculosis rarely leads to systemic infection with fever and organ related symptoms, but endocarditis [6], respiratory distress and pneumonia [7], necrotizing fasciitis, and myositis have been described due to furunculosis [8].

A particular issue in resolving furunculosis is if the causative agent is MRSA, which is resistant to the majority of antibiotics used to treat conventional staphylococcal infections, but these strains are also more virulent and cause more severe infections.

The causative agent of furunculosis, Staphylococcus aureus, is commonly found on the skin of many individuals, and it is established that about 10-20% of the population are carriers of this pathogen. It can be found on nares and nostrils, armpits, on groins, and other areas of the body, and can be transferred to other sites via finger nails, or from the nostrils. A particular issue is carriage of methicillin-resistant Staphylococcus aureus (MRSA), which is responsible for more severe infections, but also difficult to treat due to resistance to the majority of antibiotics.

Furunculosis can develop in any individual regardless of age and sex. However, it is observed that this infection most commonly develops among male teenagers and young adults.

The majority of patients who develop furuncules are healthy, and have no underlying diseases [2]. However certain predisposing factors have been identified, and include: disruption of skin integrity through breaks and injury, poor hygiene, chronic carrier state of S. aureus, obesity, increased sweating, diabetes mellitus, and other immunosuppressive disorders (such as human immunodeficiency virus (HIV) infection). Preexisting skin infections, such as atopic dermatitis, leg ulcers, chronic wounds, or abnormal follicular anatomy (for e.g. comedones in acne) also predispose individuals to furunculosis [3], and certain chemotactic defects and enzyme deficiencies, such as mannose-binding lectin deficiency, have been described as risk factors for development of this infection [4] [5].

Clustered cases may be seen among those living in crowded areas with relatively poor hygiene, or among those who were in close contact with individuals with active infection. Hot and humid climates also contribute to the development of furuncles.

Disruption of normal skin integrity is thought to be the key in the pathogenesis of furunculosis. Namely, through cuts and breaks in the skin bacteria can penetrate tissue more easily, and descend into the wall of the hair follicle. Once bacteria reach the follicle, inflammation and infection occurs, leading to the formation of folliculitis, and accompanying inflammation of adjacent tissue leads to the development of furuncles. By definition, furunculosis develops in preexisting folliculitis, and leads to formation of abscess at the site of infection. The abscess consists of a fibrin wall surrounded by inflammatory tissue enclosing a central core of pus filled with bacteria and their products, as well as migrating leukocytes. Once the formation of abscesses occur, a potential risk of severe infection through hematogenous spread may occur, and cause infections in other organs, such as endocarditis, glomerulonephritis, osteomyelitis, arthritis, and can even reach the central nervous system and cause meningitis. It is important to mention that even smaller abscesses can be a source of systemic infection, which can be life threatening, but this is a rare occurrence.

In the case of furunculosis, prevention may play a key role in reducing the burden caused by this infection. Since poor hygiene is considered to be a major risk factor for the development of furuncles, preventive educational information on personal hygiene, and appropriate wound care are highly recommended for all individuals, especially for those with virtually any type of skin infections, including furunculosis [13] [14]. Proper hygiene is very effective, and primarily involves good personal hygiene with regular bathing, and hand-washing with soap and water, and cleansing with an alcohol-based hand gel after being in contact with infected skin or wounds. Sharing of items used on infected skin, such as razors, towels, linen, etc. should be avoided, and individuals should minimize close contact with wounds and injured skin of others.

Diet has also been mentioned as a potential risk factor, and the hypothesis of increased intake of sugars making individuals more susceptible to furunculosis is a topic of numerous research papers. These suggest that a controlled intake of sugars may decrease the risk of this infection.

Furunculosis is a skin infection due to Staphylococcus aureus in virtually all cases. This infection involves the hair follicle and adjacent tissue. Furunculosis may occur in individuals of any age and sex, but most commonly occurs among young males, and rarely appears before puberty. Infection occurs due to penetration of bacteria into previously damaged skin, or other predisposing factors (such as diabetes mellitus, or poor hygiene), leading to inflammation and abscess formation [1]. The characteristic lesion - furuncle (also known as boil) - presents as a single firm, erythematous, tender nodule that can be up to a few centimeters in diameter, which arises from the hair follicle. It can appear in any hair-bearing area, the most common being the head, neck, the axilla, and the gluteal region. Diagnosis is achieved by recognizing the skin lesion on physical examination, and workup should include swab cultures to identify the causative agent. Additional tests should be done to rule out any underlying causes that may predispose patients to this condition. Furuncles may resolve spontaneously, but treatment can be sometimes necessary, and comprises local therapy, including incision and drainage of abscesses and warm compresses, and antibiotics if the infection is severe. Furunculosis resolves with therapy in most cases, but recurrent furunculosis, formation of carbuncles (coalescence of several furuncles, which can lead to scarring and deeper infection) or systemic infection may arise as complications if not treated properly.

Furunculosis is a bacterial infection of the skin. Furuncles are small, red, tender and initially superficial collections of pus that are called abscesses and cause inflammation of the hair follicle and the adjacent tissue. Several risk factors, such as poor hygiene and skin care, as well as underlying ilnesses such as diabetes mellitus, or other immunosuppressive diseases predispose individuals to this infection. It most commonly affects young males, and typical occurs on the neck, face, groins and buttocks. They are uncomfortable and may be very painful when closely attached to underlying structures (for example, on the nose, ears, or fingers). If furunculosis does not resolve spontaneously, or with therapy, bacteria may spread from this lesion to infect the surrounding tissue, which may cause a more severe infection with symptoms such as fever and malaise, requiring therapy with antibiotics. However, furuncles are usually treated with local application of warm compresses and incision of these abscesses, as well as drainage of accumulated pus. This procedure is performed exclusively by medical personnel, and should never be attempted at home. Local therapy is usually effective, and resolves the infection in most cases. If not, antibiotic therapy, depending upon the antibiotic to which the bacterial organism is most susceptible should be given. It is important to mention that hygiene and sanitary measures are crucial in preventing this skin infection, through regular bathing, hand-washing, and cleansing of affected skin area, because furunculosis may be recurrent, and cause chronic skin issues, which may be debilitating.

1. Dahl MV. Strategies for the management of recurrent furunculosis. South Med J. 1987 Mar;80(3):352-6.
2. Hoeger PH. Antimicrobial susceptibility of skin-colonizing S. aureus strains in children with atopic dermatitis. Pediatr Allergy Immunol. 2004 Oct;15(5):474-7.
3. Demirçay Z, Ekşioğlu-Demiralp E, Ergun T, Akoğlu T. Phagocytosis and oxidative burst by neutrophils in patients with recurrent furunculosis. Br J Dermatol. 1998 Jun;138(6):1036-8.
4. Gilad J, Borer A, Smolyakov R, Riesenberg K, Schlaeffer F, Levy R. Impaired neutrophil functions in the pathogenesis of an outbreak of recurrent furunculosis caused by methicillin-resistant Staphylococcus aureus among mentally retarded adults. Microbes Infect. 2006 Jun;8(7):1801-5.
5. Kars M, van Dijk H, Salimans MM, Bartelink AK, van de Wiel A. Association of furunculosis and familial deficiency of mannose-binding lectin. Eur J Clin Invest. 2005 Aug;35(8):531-4.
6. Bahrain M, Vasiliades M, Wolff M, Younus F. Five cases of bacterial endocarditis after furunculosis and the ongoing saga of community-acquired methicillin-resistant Staphylococcus aureus infections. Scand J Infect Dis. 2006;38(8):702-7.
7. Al-Tawfiq JA, Aldaabil RA. Community-acquired MRSA bacteremic necrotizing pneumonia in a patient with scrotal ulceration. J Infect. 2005 Nov;51(4):e241-3.
8. Miller LG, Perdreau-Remington F, Rieg G, Mehdi S, Perlroth J, Bayer AS, Tang AW, Phung TO, Spellberg B. Necrotizing fasciitis caused by community-associated methicillin-resistant Staphylococcus aureus in Los Angeles. N Engl J Med. 2005 Apr 7;352(14):1445-53.
9. Taira BR, Singer AJ, Thode HC Jr, Lee CC. National epidemiology of cutaneous abscesses: 1996 to 2005. Am J Emerg Med. 2009 Mar;27(3):289-92. doi: 10.1016/j.ajem.2008.02.027.
10. Nagaraju U, Bhat G, Kuruvila M, Pai GS, Jayalakshmi, Babu RP. Methicillin-resistant Staphylococcus aureus in community-acquired pyoderma. Int J Dermatol. 2004 Jun;43(6):412-4.
11. Liu C, Bayer A, Cosgrove SE, Daum RS, Fridkin SK, Gorwitz RJ, Kaplan SL, Karchmer AW, Levine DP, Murray BE, J Rybak M, Talan DA, Chambers HF; Infectious Diseases Society of America. Clinical practice guidelines by the infectious diseases society of america for the treatment of methicillin-resistant
    Staphylococcus aureus infections in adults and children. Clin Infect Dis. 2011 Feb 1;52(3):e18-55. doi: 10.1093/cid/ciq146. Epub 2011 Jan 4. Erratum in: Clin Infect Dis. 2011 Aug 1;53(3):319.
12. Stevens DL, Bisno AL, Chambers HF, et al. Practice guidelines for the diagnosis and management of skin and soft tissue infections: 2014 update by the Infectious Diseases Society of America. Clin Infect Dis 2014 ;59:e10-52.
13. Laube S, Farrell AM. Bacterial skin infections in the elderly: diagnosis and treatment. Drugs Aging. 2002;19(5):331-42.
14. Turabelidze G, Lin M, Wolkoff B, Dodson D, Gladbach S, Zhu BP. Personal hygiene and methicillin-resistant Staphylococcus aureus infection. Emerg Infect Dis. 2006 Mar;12(3):422-7.