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NHS Choices Condition

Content supplied by NHS Choices

Most boils are caused when one or more hair follicles are infected by bacteria called staphylococcus aureus, or ‘staph’ bacteria. Staph bacteria usually live on the skin and inside the throat and nose. 

Normally, the skin protects the body against bacteria. However, sometimes it is possible for staph bacteria to enter the skin through a cut or graze, or down a hair follicle (a small sac in the skin that a hair grows out of).

When the bacteria infect your skin, your immune system responds by sending white blood cells to the source of the infection, to kill the bacteria.

A combination of dead bacteria, dead white blood cells and dead skin cells build up inside the boil. This is known as pus.

Risk factors

Known risk factors (things that make you more likely to get boils) include:

  • Diabetes: the high levels of sugar in the blood, associated with diabetes, make it more difficult for your immune system to protect you against skin infection.
  • Other health conditions that weaken the immune system, such as HIV.
  • Medication that is known to weaken the immune system, such as steroids or chemotherapy.
  • Other pre-existing skin conditions, such as acne or eczema.
Back to the Embarrassing Bodies Condition Guide or view information about Boils on www.nhs.co.uk »

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The information provided on this website (including any NHS Choices medical information) is for use as information or for educational purposes only and is not a substitute for professional medical care by a qualified doctor or other qualified healthcare professional. We do not warrant that any information included within this site will meet your health or medical requirements. This Embarrassing Bodies site does not provide any medical or diagnostic services so you should always check with a health professional if you have any concerns about your health.


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