Lymph nodes are found throughout your body. They are an important part of your immune system. Lymph nodes help your body recognize and fight germs, infections, and other foreign substances.

The term "swollen glands" refers to enlargement of one or more lymph nodes.

In a child, a node is considered enlarged if it is more than 1 centimeter (0.4 inch) in diameter.

See also: Lymphadenitis and lymphangitis

Common areas where the lymph nodes can be felt (with the fingers) include:

• Groin
• Armpit
• Neck (there is a chain of lymph nodes on either side of the front of the neck, both sides of the neck, and down each side of the back of the neck)
• Under the jaw and chin
• Behind the ears
• On the back of the head

Lymph nodes can become swollen from infection, inflammatory conditions, an abscess, or cancer. Other causes of enlarged lymph nodes are rare. By far, the most common cause of swollen lymph nodes is infection.

When swelling appears suddenly and is painful, it is usually caused by injury or an infection. Enlargement that comes on gradually and painlessly may, in some cases, result from cancer or a tumor.

Infections that commonly cause swollen lymph nodes include:

• Abscessed or impacted tooth
• Ear infection
• Colds, flu, and other infections
• Gingivitis
• Mononucleosis
• Mouth sores
• Sexually transmitted diseases
• Tonsillitis
• Tuberculosis
• Skin infections

Immune or autoimmune disorders that can cause swollen lymph nodes include rheumatoid arthritis and HIV.

Cancers that can often cause swollen lymph nodes include leukemia, Hodgkin's disease, or non-Hodgkin's lymphoma. However, many other cancers may also cause this problem.

Which lymph nodes are swollen depends on the type of problem and the body parts involved. Identifying the location can help determine the possible cause.

Swollen lymph nodes may also be caused by some medications (such phenytoin for seizures) or certain vaccinations (such as typhoid immunization).