DefinitionActinomycosis is a long-term (chronic) bacterial infection that commonly affects the face and neck.Alternative NamesLumpy jawCauses, incidence, and risk factorsActinomycosis is usually caused by an anaerobic bacteria called Actinomyces israelii, which is a common and normally not disease-causing (nonpathogenic) organism found in the nose and throat.Because of the bacteria's normal location in the nose and throat, actinomycosis most commonly appears in the face and neck. However, the infection can sometimes occur in the chest (pulmonary actinomycosis), abdomen, pelvis, or other areas of the body. The infection is not contagious.Symptoms occur when the bacteria enters the facial tissues after trauma, surgery, or infection. A common triggering causes is dental abscess or oral surger