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Author: Dr Amanda Oakley Dermatologist, Hamilton, New Zealand. Updated by Dr Amanda Oakley; Vanessa Ngan, Staff Writer; June 2014. Latest update by Dr Jannet Gomez, Postgraduate Student in Clinical Dermatology, Queen Mary University, London, United Kingdom, January 2016.
A boil (also called a furuncle) is a deep form of bacterial folliculitis (infection of a hair follicle).
Boils present as one or more tender red spots, lumps or pustules. Careful inspection reveals that the boil is centred on a hair follicle. A boil is a deep form of bacterial folliculitis; superficial folliculitis is sometimes present at the same time. Staphylococcus aureus can be cultured from the skin lesions.
If there are multiple heads, the lesion is called a carbuncle. Large boils form abscesses, defined as an accumulation of pus within a cavity. Cellulitis may also occur, ie, infection of the surrounding tissues, and this may cause fever and illness.
Most people with boils are otherwise healthy and have good personal hygiene. They do however carry Staphylococcus aureus on the surface of their skin (staphylococcal carrier state). Why this occurs is usually not known, but it is estimated that 10–20% of the population are staphylococcal carriers.
Staphylococcus aureus is most commonly carried in the nostrils, armpits, between the legs and in the cleft between the buttocks. It may be transferred to other sites from the nostrils via the finger nails.
Tiny nicks or grazes or something rubbing against the skin can innoculate the bacteria into the wall of a hair follicle which is a weak point in the skin's defences. Once innoculated, the bacteria cause a boil which goes on to run its usual course of about 10 days.
Although most people with boils are otherwise healthy, boils are sometimes related to immune deficiency, anaemia, diabetes, smoking or iron deficiency.
Treatment of boils depends on their severity. Your doctor may give you specific advice and medical treatment, some are listed below:
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