Lymphadenitis is an infection of the lymph nodes (also called lymph glands). It is a common complication of certain bacterial infections.

The lymph system is a network of organs, lymph nodes, lymph ducts, and lymph vessels (or channels) that produce and move a fluid called lymph from tissues to the bloodstream. For more information on this part of the body, see lymph system.

The lymph glands, or nodes, are small structures that filter the lymph fluid. There are many white blood cells in the lymph nodes to help fight infection.

Lymphadenitis occurs when the glands become enlarged by inflammation, usually in response to bacteria, viruses, or fungi. The swollen glands are usually found near the site of an underlying infection, tumor, or inflammation.

Lymphadenitis may occur after skin infections or other bacterial infections, particularly those due to streptococcus or staphylococcus. Sometimes it is caused by rare infections such as tuberculosis or cat scratch disease (Bartonella).