Actinomycosis is a rare bacterial infection. It causes pus to collect in the body. It may start in the:

  • Jaw
  • Lungs
  • Abdomen
  • Uterus

Rarely, the infection can spread from one place in the body to another.

Abdominal Abscess

Abdominal Abscess
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Certain bacteria cause actinomycosis. They are normal in the mouth and sometimes in the bowels. They get into the body through breaks in the tissues. Tooth decay causes infections in the mouth and jaw. This is the most common type.

Risk Factors

This infection is more common in men. Actinomycosis may be more common after:

  • Problems with teeth and gums or dental work
  • Saliva, food, or drink getting into lungs
  • Long-lasting lung disease
  • Bowel surgery
  • Intrauterine device (IUD), especially if it has been in for a long time without medical check

There is also a higher risk of infection in people with:

  • Diabetes
  • Weak immune system
  • Malnourishment—problem getting proper nutrition


Symptoms depend on the where the infection starts. They may involve:

  • Swelling in the mouth, neck, or jaw
  • Pus with tiny, yellowish specks
  • Pus that drains through the skin
  • Fever
  • Weight loss
  • Cough
  • Swelling or a hard lump in the belly


The doctor will ask about your symptoms and past health. A physical exam will be done. Other tests may include:

  • Testing of fluids, pus, or phlegm
  • A biopsy—to look at the tissues


The infection is treated with antibiotics. They are often started through an IV. The antibiotics may then be taken as pills for months after.

Surgery may also be needed to remove dead or infected tissue.


Good dental care may lower the risk of infection in the jaw.


Family Doctor—American Academy of Family Physicians
Mouth Healthy—American Dental Association


Canadian Dental Association


Actinomycosis. Merck Manual Professional Version website. Available at: Accessed February 4, 2021.
Cervicofacial actinomycosis. EBSCO DynaMed website. Available at: Accessed February 4, 2021.
Moturi K, Kaila V. Cervicofacial actinomycosis and its management. Ann Maxillofac Surg. 2018;8(2):361-364.
Last reviewed March 2021 by David L. Horn, MD, FACP

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