Merck Manual

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Wingfield E. Rehmus

, MD, MPH, University of British Columbia

Reviewed/Revised Apr 2021 | Modified Sep 2022
Topic Resources

Lymphadenitis is infection of one or more lymph nodes, which usually become swollen and tender.

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 Infectious Mononucleosis Epstein-Barr virus causes a number of diseases, including infectious mononucleosis. The virus is spread through kissing. Symptoms vary, but the most common are extreme fatigue, fever, sore throat... read more Infectious Mononucleosis , cytomegalovirus infection Cytomegalovirus (CMV) Infection Cytomegalovirus infection is a common herpesvirus infection with a wide range of symptoms: from no symptoms to fever and fatigue (resembling infectious mononucleosis) to severe symptoms involving... read more , streptococcal infection Streptococcal Infections Streptococcal infections are caused by any one of several species of Streptococcus. These gram-positive, sphere-shaped (coccal) bacteria (see figure ) cause many disorders, including... read more , tuberculosis Tuberculosis (TB) Tuberculosis is a chronic contagious infection caused by the airborne bacteria Mycobacterium tuberculosis. It usually affects the lungs, but almost any organ can be involved. Tuberculosis... read more Tuberculosis (TB) , or syphilis Syphilis Syphilis is a sexually transmitted infection caused by the bacteria Treponema pallidum. It can occur in three stages of symptoms, separated by periods of apparent good health. Syphilis... read more Syphilis . The infection may affect many lymph nodes or only those in one area of the body.

Symptoms of Lymphadenitis

Diagnosis of Lymphadenitis

  • A doctor's evaluation

  • Sometimes aspiration and culture or a tissue biopsy

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 doctor inserts a needle into a lymph node and withdraws (aspirates) fluid. The fluid sample is then sent to a laboratory for culture (the sample is placed in a culture medium that allows microorganisms to grow). The culture can identify the organism causing the infection. Alternatively, the doctor can do a biopsy (removal and examination of a piece of the lymph node under a microscope).

Treatment of Lymphadenitis

  • Antibiotics

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.

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