Actinomycosis

Actinomycosis is an uncommon infection caused by bacteria that normally live harmlessly in the mouth, gut and genital tract. It develops when they get into deeper tissue, for example after dental problems or surgery. It grows slowly and can look like other conditions at first.

Last updated Nov 9, 2026

What it is

It most often affects the face and neck, but can also affect the lungs, the abdomen or the pelvis (sometimes linked to a long-term coil).

It is treated with antibiotics, usually for weeks or months, and sometimes surgery to drain abscesses.

Common signs

  • A firm lump in the jaw, neck or elsewhere that grows slowly
  • Abscesses or openings in the skin that leak pus
  • Fever, tiredness and weight loss

How it is usually diagnosed

  • Samples of pus or tissue examined in the laboratory
  • Scans such as CT to see how far it has spread

Records worth keeping

Keeping these together makes each appointment easier, especially when you see a new doctor:

  • Laboratory and biopsy reports
  • Scan reports
  • The antibiotics you took, with start and end dates
  • Dental records if the infection started in the mouth

Questions to ask your doctor

  • How long will I need antibiotics?
  • How will we know the infection has cleared?
  • Is there anything that might have caused it that we should deal with?

When to get help right away

Call 112 or go to the nearest emergency department if you have:

  • High fever with feeling very unwell, confused or breathing fast
  • Swelling in the neck that makes breathing or swallowing hard

This page is general information. It is not a diagnosis and does not replace a doctor who knows your history. Medfold keeps your records organised; it does not interpret them.

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