What are lymph nodes?

Lymph nodes are small, bean-shaped glands throughout the body. They are part of the lymphatic system, which carries fluid (lymph fluid), nutrients, and waste material between the body tissues and the bloodstream.

The lymphatic system is an important part of the immune system, the body's defense system against disease. The lymph nodes filter lymph fluid as it flows through them, trapping bacteria, viruses, and other foreign substances, which are then destroyed by special white blood cells called lymphocytes.

Lymph nodes may be found singly or in groups, and they may be as small as the head of a pin or as large as an olive. Groups of lymph nodes can be felt in the neck, groin, and underarms. Lymph nodes generally are not tender or painful. Most lymph nodes in the body cannot be felt.

What causes swollen lymph nodes?

Lymph nodes often swell in one location when a problem such as an injury, infection, or tumor develops in or near the lymph node. Which lymph nodes are swollen can help identify the problem.

• The glands on either side of the neck, under the jaw, or behind the ears commonly swell when you have a cold or sore throat. Glands can also swell following an injury, such as a cut or bite, near the gland or when a tumor or infection occurs in the mouth, head, or neck.
• Glands in the armpit (axillary lymph nodes) may swell from an injury or infection to the arm or hand. A rare cause of axillary swelling may be breast cancer or lymphoma.
• The lymph nodes in the groin (femoral or inguinal lymph nodes) may swell from an injury or infection in the foot, leg, groin, or genitals. In rare cases, testicular cancer, lymphoma, or melanoma may cause a lump in this area.
• Glands above the collarbone (supraclavicular lymph nodes) may swell from an infection or tumor in the areas of the lungs, breasts, neck, or abdomen.

Common sites for swollen lymph nodes include the neck, groin, and underarms.

What does it mean when lymph nodes swell in two or more areas of the body?

When lymph nodes swell in two or more areas of the body, it is called generalized lymphadenopathy. This may be caused by:

• A viral illness, such as measles, rubella, chickenpox (varicella), or mumps.
• Mononucleosis (Epstein-Barr virus), which results in fever, sore throat, and fatigue, or cytomegalovirus (CMV), a viral infection that causes symptoms similar to those of mononucleosis.
• A bacterial illness, such as strep throat (caused by the streptococcus bacterium) or Lyme disease (a bacterial infection spread by certain types of ticks).
• Side effects of phenytoin (Dilantin), a medication used to prevent seizures.
• Side effects of measles-mumps-rubella (MMR) vaccination.
• Cancer, such as leukemia, Hodgkin's disease, and non-Hodgkin's lymphoma.
• Acquired immunodeficiency syndrome (AIDS), which develops after contracting HIV (human immunodeficiency virus). This virus attacks the immune system, making it difficult for the body to fight off infection and some disease.
• Syphilis, a sexually transmitted disease.

How are swollen lymph nodes treated?