Lymphadenitis involves inflammation of the lymph glands. This may occur if the glands are overwhelmed by bacteria, virus, fungi, or other organisms and infection develops within the glands. It may also occur as a result of circulating cancer cells or other inflammatory conditions. The location of the affected gland(s) is usually associated with the site of the underlying infection, tumour, or inflammation. It commonly is a result of a cellulitis or other bacteria infection (usually infection by streptococci or staphylococci).
Lymphangitis involves the lymph vessels/channels, with inflammation of the channel and resultant pain and systemic and localized symptoms. It commonly results from an acute streptococcal or staphylococcal infection, such as from an insect or animal bite or sting. Lymphangitis may resemble thrombophlebitis.