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  • Painful
  • small
  • rough skin growth

A boil, also called a furuncle, is a deep folliculitis, infection of the hair follicle.[1]

It is most commonly caused by infection by the bacterium Staphylococcus aureus, resulting in a painful swollen area on the skin caused by an accumulation of pus and dead tissue.[2] Individual boils clustered together are called carbuncles.[1] Most human infections are caused by coagulase-positive S. aureus strains, notable for the bacteria's ability to produce coagulase, an enzyme that can clot blood. Almost any organ system can be infected by S. aureus.

Signs and symptoms

Boils are bumpy, red, pus-filled lumps around a hair follicle that are tender, warm, and painful. They range from pea-sized to golf ball-sized. A yellow or white point at the center of the lump can be seen when the boil is ready to drain or discharge pus. In a severe infection, an individual may experience fever, swollen lymph nodes, and fatigue. A recurring boil is called chronic furunculosis.[2][3][4][5] Skin infections tend to be recurrent in many patients and often spread to other family members. Systemic factors that lower resistance commonly are detectable, including: diabetes, obesity, and hematologic disorders.[6] Boils can be caused by other skin conditions that cause the person to scratch and damage the skin.[citation needed]

Boils may appear on the buttocks or near the anus, the back, the neck, the stomach, the chest, the arms or legs, or even in the ear canal.[7] Boils may also appear around the eye, where they are called styes.[8] A boil on the gum is called intraoral dental sinus, or more commonly, a gumboil.[citation needed]


The most common complications of boils are scarring and infection or abscess of the skin, spinal cord, brain, kidneys, or other organs. Infections may also spread to the bloodstream (bacteremia) and become life-threatening.[4][5] S. aureus strains first infect the skin and its structures (for example, sebaceous glands, hair follicles) or invade damaged skin (cuts, abrasions). Sometimes the infections are relatively limited (such as a stye, boil, furuncle, or carbuncle), but other times they may spread to other skin areas (causing cellulitis, folliculitis, or impetigo). Unfortunately, these bacteria can reach the bloodstream (bacteremia) and end up in many different body sites, causing infections (wound infections, abscesses, osteomyelitis, endocarditis, pneumonia)[9] that may severely harm or kill the infected person. S. aureus strains also produce enzymes and exotoxins that likely cause or increase the severity of certain diseases. Such diseases include food poisoning, septic shock, toxic shock syndrome, and scalded skin syndrome.[10] Almost any organ system can be infected by S. aureus. Squeezing or cutting boils in the danger triangle of the face can be particularly dangerous if done outside a medical setting, as blood vessels in this area drain into the brain and can carry serious infections there.[citation needed]

When burst, a seemingly solid, whitish colored pus initially appears then the pus and some blood follows.[citation needed]



Naturally the cause is bacteria such as staphylococci that are present on the skin. Bacterial colonisation begins in the hair follicles and can cause local cellulitis and inflammation.[2][4][5] Myiasis caused by the tumbu fly in Africa usually presents with cutaneous furuncles.[11] Risk factors for furunculosis include bacterial carriage in the nostrils, diabetes mellitus, obesity, lymphoproliferative neoplasms, malnutrition, and use of immunosuppressive drugs.[12]

Family history

People with recurrent boils are as well more likely to have a positive family history, take antibiotics, and to have been hospitalised, anemic, or diabetic; they are also more likely to have associated skin diseases and multiple lesions.[13]


Other causes include poor immune system function such as from HIV/AIDS, diabetes, malnutrition, or alcoholism.[14] Poor hygiene and obesity have also been linked.[14] It may occur following antibiotic use due to the development of resistance to the antibiotics used.[15] An associated skin disease favors recurrence. This may be attributed to the persistent colonization of abnormal skin with S. aureus strains, such as is the case in persons with atopic dermatitis.[15] Boils which recur under the arm, breast or in the groin area may be associated with hidradenitis suppurativa (HS).[16]


Diagnosis is made through clinical evaluation by a physician, which may include culturing of the lesion.[17]


A boil may clear up on its own without bursting, but more often it will need to be opened and drained. This will usually happen spontaneously within two weeks. Regular application of a warm moist compress, both before and after a boil opens, can help speed healing. The area must be kept clean, hands washed after touching it, and any dressings disposed of carefully, in order to avoid spreading the bacteria. A doctor may cut open or "lance" a boil to allow it to drain, but squeezing or cutting should not be attempted at home, as this may further spread the infection. Antibiotic therapy may be recommended for large or recurrent boils or those that occur in sensitive areas (such as the groin, breasts, armpits, around or in the nostrils, or in the ear).[2][3][4][5] Antibiotics should not be used for longer than one month, with at least two months (preferably longer) between uses, otherwise it will lose its effectiveness.[18] If the patient has chronic (more than two years) boils, removal by plastic surgery may be indicated.[citation needed]

Furuncles at risk of leading to serious complications should be incised and drained if antibiotics or steroid injections are not effective. These include furuncles that are unusually large, last longer than two weeks, or occur in the middle of the face or near the spine.[2][5] Fever and chills are signs of sepsis and indicate immediate treatment is needed.[19]

Staphylococcus aureus has the ability to acquire antimicrobial resistance easily, making treatment difficult. Knowledge of the antimicrobial resistance of S. aureus is important in the selection of antimicrobials for treatment.[20]

See also


  1. 1.0 1.1 1.2 James, William D.; Elston, Dirk; Treat, James R.; Rosenbach, Misha A.; Neuhaus, Isaac (2020). "14. Bacterial infections". Andrews' Diseases of the Skin: Clinical Dermatology (13th ed.). Edinburgh: Elsevier. p. 255-256. ISBN 978-0-323-54753-6. Archived from the original on 7 June 2022. Retrieved 29 May 2022.
  2. 2.0 2.1 2.2 2.3 2.4 MedlinePlus Encyclopedia: Furuncle
  3. 3.0 3.1 Blume JE, Levine EG, Heymann WR (2003). "Bacterial diseases". In Bolognia JL, Jorizzo JL, Rapini RP (eds.). Dermatology. Mosby. p. 1126. ISBN 0-323-02409-2.
  4. 4.0 4.1 4.2 4.3 Habif, TP (2004). "Furuncles and carbuncles". Clinical Dermatology: A Color Guide to Diagnosis and Therapy (4th ed.). Philadelphia PA: Mosby.
  5. 5.0 5.1 5.2 5.3 5.4 Wolf K; et al. (2005). "Section 22. Bacterial infections involving the skin". Fitzpatrick's Color Atlas & Synopsis of Clinical Dermatology (5th ed.). McGraw-Hill.
  6. Steele RW, Laner SA, Graves MH (February 1980). "Recurrent staphylococcal infection in families". Arch Dermatol. 116 (2): 189–90. doi:10.1001/archderm.1980.01640260065016. PMID 7356349. Archived from the original on 28 August 2021. Retrieved 5 June 2021.
  7. "Boils, Carbuncles and Furunculosis". Archived from the original on 7 June 2015. Retrieved 26 July 2014.
  8. "Boils, Kidshealth". 13 September 2011. Archived from the original on 1 July 2014. Retrieved 26 July 2014.
  9. Lina G, Piémont Y, Godail-Gamot F, Bes M, Peter MO, Gauduchon V, Vandenesch F, Etienne J (November 1999). "Involvement of Panton-Valentine leukocidin-producing Staphylococcus aureus in primary skin infections and pneumonia". Clin Infect Dis. 29 (5): 1128–32. doi:10.1086/313461. PMID 10524952.
  10. "Staph Infection Causes, Symptoms, Treatment – Staph Infection Diagnosis". eMedicineHealth. Archived from the original on 24 December 2017. Retrieved 5 June 2021.
  11. Tamir J, Haik J, Schwartz E (2003). "Myiasis with Lund's fly (Cordylobia rodhaini) in travellers". J Travel Med. 10 (5): 293–95. doi:10.2310/7060.2003.2732. PMID 14531984.
  12. Scheinfeld NS (2007). "Furunculosis". Consultant. 47 (2). Archived from the original on 23 November 2012. Retrieved 5 June 2021.
  13. El-Gilany AH, Fathy H (January 2009). "Risk factors of recurrent furunculosis". Dermatol Online J. 15 (1): 16. PMID 19281721. Archived from the original on 3 May 2013. Retrieved 5 June 2021.
  14. 14.0 14.1 Demos, M; McLeod, MP; Nouri, K (October 2012). "Recurrent furunculosis: a review of the literature". The British Journal of Dermatology. 167 (4): 725–32. doi:10.1111/j.1365-2133.2012.11151.x. PMID 22803835. S2CID 25415894.
  15. 15.0 15.1 Laube S, Farrell M (2002). "Bacterial skin infection in the elderly: diagnosis and treatment". Drugs & Aging. 19 (5): 331–42. doi:10.2165/00002512-200219050-00002. PMID 12093320. S2CID 24264303.
  16. "What is this boil like abscess under your arm, breast or groin". The Hidradenitis Suppurativa Trust. Archived from the original on 29 September 2015. Retrieved 28 September 2015.
  17. "Furuncles and Carbuncles". Merck Manuals. August 2017. Archived from the original on 1 November 2019. Retrieved 29 April 2018.
  18. Mayo Clinic Archived 15 August 2012 at the Wayback Machine
  19. "Archived copy". Archived from the original on 15 August 2012. Retrieved 14 August 2012.{{cite web}}: CS1 maint: archived copy as title (link)
  20. Nagaraju U, Bhat G, Kuruvila M, Pai GS, Babu RP (2004). "Methicillin-resistant staphylococcus aureus in community-acquired pyoderma". Int J Dermatol. 43 (6): 412–14. doi:10.1111/j.1365-4632.2004.02138.x. PMID 15186220. S2CID 38742158.

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