When people have mildly swollen lymph nodes, they may not be able to tell, but occasionally the lymph nodes will swell to a point when they feel hard or can be felt with a light touch. There are several places to check to see if nodes feel enlarged: right under the jaw line and around the throat, in the underarms, and on both sides of the groin. It is advised that people not poke and prod these areas, however, since this might irritate the nodes further. If a light touch causes pain or can clearly feel hardened or swollen nodes, it's usually time to check this out with a doctor, especially if other symptoms of illness are present or if only one or two nodes are very enlarged.
The human body has more than 600 lymph nodes, and these are important disease fighting agents. They are a network of cells that contain lymphocytes and macrophages, white blood cells that attack disease in the body and break it down for disposal. When lymph nodes must go into action to fight a virus, bacterial infection or some other presence of foreign cells, they may swell. They go from being about pea-sized in diameter to slightly larger or greatly larger than this, and they can feel hard or be painful to touch.
Generally, you should contact a doctor if a lymph node feels larger than 0.5 inch (1.27 cm) across and remains so for at least a month, or if it is more than 1 inch (2.54 cm) across. If swollen nodes are present with high fever, extreme sore throat, rash, or redness over the node, this is also indication to contact a physician. Those at risk for illnesses due to an immunodeficiency or autoimmune condition may have a different protocol for when to contact doctors, and sudden swollen nodes in children ought to be cause for concern sooner.
When swollen lymph nodes exist, they can indicate minor or serious illnesses. It's common when people have conditions like mononucleosis to have lymph node swelling around the throat, and the skin over the nodes might be red in color. Mono is accompanied by extreme fatigue and usually very sore throat, and it's important to get this condition diagnosed.
Swollen lymph nodes may also indicate presence of bacterial infection like strep throat or septicemia, an infection of the blood. There are other conditions that can cause the lymph nodes to swell, including cancer of certain sorts — especially lymphatic cancer — HIV, and some parasitic infections. Conditions like cat scratch fever can lead to chronic swelling of the lymph nodes, especially in kids.