(See also Overview of Bacterial Skin Infections.)
Lymphadenitis is infection of one or more lymph nodes, which usually become swollen and tender.
Lymphadenitis almost always results from an infection, which may be caused by bacteria, viruses, protozoa, or fungi. Typically, the infection spreads to a lymph node from a skin, ear, nose, or eye infection or from such infections as infectious mononucleosis, cytomegalovirus infection, streptococcal infection, tuberculosis, or syphilis. The infection may affect many lymph nodes or only those in one area of the body.
Infected lymph nodes enlarge and are usually tender and painful. Sometimes, the skin over the infected nodes is inflamed, looks red, and feels warm. Some people may have cellulitis. People commonly have a fever. Occasionally, pockets of pus (abscesses) develop. Enlarged lymph nodes that do not cause pain, tenderness, or redness may indicate a serious different disorder, such as lymphoma, tuberculosis, or Hodgkin lymphoma. Such lymph nodes require a doctor’s attention.
Usually, lymphadenitis can be diagnosed on the basis of symptoms, and its cause is an obvious nearby infection. When the cause cannot be identified easily, a biopsy (removal and examination of a tissue sample under a microscope) and a culture (a sample is sent to a laboratory and placed in a culture medium that allows microorganisms to grow) may be needed to confirm the diagnosis and to identify the organism causing the infection.
Treatment depends on the organism causing the infection. For a bacterial infection, an antibiotic is usually given by vein (intravenously) or by mouth. Hot, wet compresses may help relieve the pain in inflamed lymph nodes. Usually, once the infection has been treated, the lymph nodes slowly shrink, and the pain subsides. Sometimes the enlarged nodes remain firm but no longer feel tender. Abscesses must be drained surgically.