(See also Overview of Bacterial Skin Infections.)
Lymph is a fluid that oozes out of the body's tiniest blood vessels. The fluid goes between cells and brings nourishment and carries away damaged cells, cancer cells, and infectious microorganisms. All lymph passes through lymphatic vessels to strategically placed lymph nodes. Lymph nodes filter damaged cells, cancer cells, and foreign particles out of the lymph fluid. Special white blood cells in lymph nodes engulf and destroy damaged cells, cancer cells, infectious organisms, and foreign particles.
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 based on the 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 make the diagnosis because there are other disorders that cause swollen lymph nodes. Also, the culture can identify the organism causing the infection.
Treatment of lymphadenitis depends on the organism causing the infection. For a bacterial infection, an antibiotic is usually given by vein (intravenously) or by mouth. Other drugs are given for a fungal or parasitic infection.
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, and people are given intravenous antibiotics. In children, intravenous antibiotics are commonly needed.