Boil or furuncle is a skin disease caused by the inflammation of hair follicles, thus resulting in the localized accumulation of pus and dead tissue. Individual boils can cluster together and form an interconnected network of boils called carbuncles. In severe cases, boils may develop to form abscesses.

Staphylococcus aureus was discovered in late 1870’s by Alexander Ogston, a surgeon at the Aberdeen Royal Infirmary. It was discovered to be the major cause of skin and soft tissue infections such as boils, staphylococcal scalded skin syndrome and impetigo^{[1] [2]}. Carl Alois Philipp Garrè was a Swiss surgeon who proved that Staphylococcus aureus causes carbuncles and boils by self experimentation. Dr. Garre discovered and named Garre’s sclerosing osteomyelitis (sclerosing osteitis – form of chronic osteomyelitis with proliferative periostitis).^[3]

Boil (furuncle) may be classified according to the International Classification of Diseases (ICD-10) based on anatomical location.^[4] Based on the duration of symptoms, boils may be classified into acute and chronic.

Boil (furuncle) is a localized deep suppurative necrotizing form of folliculitis which involves the dermis and the subcutaneous tissue. Staphylococcus aureus is the most common causative agent. Following an abrasion or cut, the pathogen uses the wound site to invade and colonize the hair follicle. This leads to the formation of tender, erythematous, perifollicular nodule. The boil later becomes painful and fluctuant leading to discharge of pus and formation of necrotic plugs, which may leave a scar.^[5]

Boils (furuncles) are generally caused by an infection of the hair follicles by Staphylococcus aureus or Staphylococcus epidermidis.

Boil (furuncle) must be differentiated from other common diseases that cause tender swelling or a reddened lump filled with pus such as cystic acne, hydradrenitis suppurativa, and pilonidal cyst.^[6]

The incidence and prevalence of boils (furuncles) is uncertain. In England, between 2002-2003, boils and carbuncles were responsible for approximately 190 out of 100,000 hospital visits^[7]. Patients with all age groups can develop boils(furuncles). Boils(furuncles) is common among teenagers and young adults.

Common risk factors in the development of boils include immunosupression, malnutrition, coexisting skin conditions, and poor hygiene.

According to the U.S. Preventive Service Task Force (USPSTF), there is insufficient evidence to recommend routine screening for furunculosis.

If left untreated, patients with boils (furuncles) may progress to develop carbuncles, fever, and lymphadenopathy. The most common complications of boils include scarring and recurrence. Other complications include septicemia leading to abscess of spinal cord, brain, kidneys, or other organs. The prognosis is generally good, however, it varies with underlying risk factors.

A detailed and thorough history from the patient is necessary. Specific areas of focus when obtaining a history from the patient include history of immunosupression, family history of furunculosis, history of contact sports, history of close contact, and recent travel. Common symptoms of the boil include firm, red, and painful bump with pus filled head.^[8][9][8]

Patients with boils usually appear normal. However, the appearance varies with the associated risk factors.

The following are the images associated with boils on extremities.

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  url = http://www.atlasdermatologico.com.br/disease.jsf?diseaseId=159>
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  url = http://www.atlasdermatologico.com.br/disease.jsf?diseaseId=159>
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  url = http://www.atlasdermatologico.com.br/disease.jsf?diseaseId=159>
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  url = http://www.atlasdermatologico.com.br/disease.jsf?diseaseId=159>
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  url = http://www.atlasdermatologico.com.br/disease.jsf?diseaseId=159>
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  url = http://www.atlasdermatologico.com.br/disease.jsf?diseaseId=159>

Laboratory study which is consistent with the diagnosis of boils include the pus culture.

X ray may be performed to detect internal abscess and osteomyelitis.

Other diagnostic studies of boils include blood analysis, urine analysis, and biopsy.

The mainstay of therapy for mild furuncles is incision and drainage only. Antimicrobial therapies are indicated in moderate and severe furuncles. Empiric antimicrobial therapies for furuncle include either TMP-SMX or Doxycycline for moderate furuncles, and either Vancomycin, Daptomycin, Linezolid, Telavancin, or Ceftaroline for severe furuncles.^[10][11]

Incision and drainage is indicated if the boil is deep large and persistent despite medical therapy.^[12]

Primary prevention

Effective measures for primary prevention of boils include hand washing, antibacterial soaps, maintain proper hygiene (hand sanitizers, antiseptic washes), avoid close contact (homeless shelters, military, prisons).

Secondary prevention

Secondary prevention strategies following boils are warm moist compresses on the boil, hand washing, and proper wound care.

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Staphylococcus aureus was discovered in late 1870’s by Alexander Ogston, a surgeon at the Aberdeen Royal Infirmary. It was discovered to be the major cause of skin and soft tissue infections such as boils, staphylococcal scalded skin syndrome and impetigo.^{[1] [2]} Carl Alois Philipp Garrè was a Swiss surgeon who proved that Staphylococcus aureus causes carbuncles and boils by self experimentation. Dr. Garre discovered and named Garre’s sclerosing osteomyelitis (sclerosing osteitis – form of chronic osteomyelitis with proliferative periostitis).^[3]

• Staphylococcus aureus was discovered in late 1870’s by Alexander Ogston, a surgeon at the Aberdeen Royal Infirmary. It was the major cause of skin and soft tissue infections such as boils, staphylococcal scalded skin syndrome, and impetigo.^{[1] [2]}
• Carl Alois Philipp Garre was a Swiss surgeon who proved that Staphylococcus aureus causes carbuncles and boils by self-experimentation. Dr. Garre discovered and named Garre’s sclerosing osteomyelitis (sclerosing osteitis – form of chronic osteomyelitis with proliferative periostitis).^[3]

Boils (furuncles) may be classified according to the International Classification of Diseases (ICD-10) based on anatomical location.^[1]

Boil (furuncle) may be classified according to the International Classification of Diseases (ICD-10) based on anatomical location:^[1][2]

• Furuncle of face
• Furuncle of neck
• Furuncle of trunk
• Furuncle of buttock
• Furuncle of limb
• Furuncle of hand
• Furuncle of foot
• Furuncle of other sites
• Furuncle, unspecified

Based on the duration of symptoms, boils may be classified into:^[3]

• Acute
• Chronic

Boils (furuncles) are a localized deep suppurative necrotizing form of folliculitis which involve the dermis and the subcutaneous tissue. Staphylococcus aureus is the most common causative agent. Following an abrasion or cut, the pathogen uses the wound site to invade and colonize the hair follicle. This leads to the formation of tender, erythematous, perifollicular nodule. The boil later becomes painful and fluctuant leading to discharge of pus and formation of necrotic plugs, which may leave a scar.^[1]

• Boil (furuncle) is a localized deep suppurative necrotizing form of folliculitis which involves the dermis and the subcutaneous tissue. Staphylococcus aureus is the most common causative agent.
• Following abrasion or cut the pathogen uses the wound site to invade and colonize the hair follicle. This leads to the formation of a tender erythematous perifollicular nodule.
• Boils may become painful and fluctuant, leading to the discharge of pus and formation of necrotic plugs, which may leave a scar.^[1]
• Furunculosis is the acute or chronic appearance of a number of boils (furuncles) at multiple skin sites. Recurrent furunculosis is defined as three or more attacks within a 12 month period.^[1]
• It is a contagious condition, which usually develops in moist or sweaty areas such as the scalp, face, buttocks, axillae, and areas that are subject to friction and perspiration.

• A group of furuncles coalesce to form a carbuncle.

• 
  Boil(furuncle)pathogenesis

• Folliculitis
• Carbuncle

On gross pathology, characteristic findings of boils include firm, tender, red, dome shaped nodules, which progress to fluctuant, pus-filled, and painful lesions. Boils may vary in size.

On microscopic histopathological analysis, characteristic findings of boils include:

• Infiltrate predominantly consists of neutrophils within the wall and ostia of hair follicles
• Lesions may subsequently be infiltrated with lymphocytes and macrophages creating a central focus of necrosis.
• Inflammation of hair follicle may be:

• Superficial (primarily involving the infandibulum)
• Deep

The following are images associated with boil:

• 
  Boil(furuncle) on Anterior leg: Dome shaped pus filled boil(furuncle) with erythema of skin – By The original uploader was Mahdouch at French Wikipedia – Transferred from fr.wikipedia to Commons., CC BY 1.0, https://commons.wikimedia.org/w/index.php?curid=3123389

Boils (furuncles) are generally caused by an infection of the hair follicles by Staphylococcus aureus or Staphylococcus epidermidis.

Common causes of boils include:^[1]

Bacteria:

• Staphylococcus aureus is the most common cause of furunculosis.

• Colonization of Staphylococcus aureus in the anterior nares and in the warm, moist skin folds such as behind ears, under pendulous breasts and in the groin plays a definitive role in the etiology of chronic or recurrent furunculosis.^[2]

• Infection with Methicillin resistant staphylococcus aureus is the leading cause of morbidity and mortality in patients with furunculosis.^[3]

Other bacterial causes:

• Enterobacteriaceae
• Enterococci
• Corynebacterium
• Streptococcus epidermidis
• Streptococcus pyogenes
• Pseudomonas Aeruginosa

Fungal causes

• Candida
• Pityrosporum species

Other causes

• Ingrown hair
• Blocked glands

Boil (furuncle) must be differentiated from other common diseases that cause tender swelling or a reddened lump filled with pus such as cystic acne, hydradrenitis suppurativa, and pilonidal cyst.^[1]

Boils must be differentiated from:^[1]

The incidence and prevalence of boils (furuncles) is uncertain. In England, between 2002-2003, boils and carbuncles were responsible for approximately 190 out of 100,000 hospital visits^[1]. Patients in all age groups can develop furuncles; however, they are common among teenagers and young adults.

• In England, between 2002-2003, boils and carbuncles were responsible for approximately 190 out of 100,000 hospital visits^[1]

• Patients of all age groups may develop furuncles. However, furuncles most commonly occur in teenagers and young adults.
• Recurrent boils cause significant mortality and morbidity among adult population in both developed and developing countries.

Furuncles affect men and women equally.

There is no racial predilection to boils.

Common risk factors in the development of boils include immunosupression, malnutrition, coexisting skin conditions, and poor hygiene.

Common risk factors in the development of boils include:

• Immunosupression^[1]

• HIV
• Diabetes
• Chemotherapy
• Corticosteroid therapy
• Immunodeficiency

• Obesity
• Sports

• Athletes participating in contact sports and using shared equipment

• Malnutrition
• Coexisting skin conditions

• Eczema, scabies and other pruritic conditions^[2]

• Staphylococcal carriers^[3]

• Most common site: anterior nares^[4][5][2]

• Poor hygiene
• People living in close contact

• Low socioeconomic status
• living in military barracks, homeless shelters, or prison

• Recent travel

According to the U.S. Preventive Service Task Force (USPSTF), there is insufficient evidence to recommend routine screening for furunculosis.

According to the U.S. Preventive Service Task Force (USPSTF), there is insufficient evidence to recommend routine screening for furunculosis.

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If left untreated, patients with boils (furuncles) may progress to develop carbuncles, fever, and lymphadenopathy. The most common complications of boils include scarring and recurrence. Other complications include septicemia leading to abscess of spinal cord, brain, kidneys, or other organs. The prognosis is generally good, however, it varies with underlying risk factors.

• If left untreated, patients with boils may progress to develop carbuncles, fever and lymphadenopathy. The most common complications of boils include scarring and recurrence. Other rare complications are bacteremia, fever, and abscess of spinal cord, brain, kidneys, or other organs.
• Recurrent furunculosis is commonly caused by methicillin susceptible staphylococcus aureus however Panton-Valentine leukocidin staphylococcus aureus (PVL-SA) and community acquired MRSA (CA-MRSA) is the leading cause of severe infection.^[1][2][3]

Common complications of furuncles include:^{[4][2][5][6][7]}

• Permanent scarring
• Recurrence
• Abscess of the skin, spinal cord, brain, kidneys, or other organ
• Endocarditis
• Osteomyelitis
• Sepsis
• Infection of brain
• Infection of spinal cord
• Spread of infection to other parts of body or skin surfaces

• Prognosis is generally good and a full recovery is expected.^[6]
• The prognosis varies with underlying risk factors or subsequent complications.