Swollen lymph nodes usually occur as a result of exposure to bacteria or viruses. When swollen lymph nodes are caused by an infection, this is known as lymphadenitis (lim-fad-uh-NIE-tis). Rarely, swollen lymph nodes are caused by cancer.

Your lymph nodes, also called lymph glands, play a vital role in your body's ability to fight off viruses, bacteria and other causes of illnesses. Common areas where you might notice swollen lymph nodes include your neck, under your chin, in your armpits and in your groin.

In some cases, the passage of time and warm compresses may be all you need to treat swollen lymph nodes. Treatment for lymphadenitis depends on the cause.

Source: http://www.mayoclinic.com

Your lymphatic system comprises a network of organs, vessels and numerous lymph nodes situated throughout your body. Most of your lymph nodes are located in your head and neck region. Lymph nodes that frequently swell are in this area, as well as in your armpits and groin area.

Swollen lymph nodes are a sign that something is wrong somewhere in your body. When your lymph nodes first swell, you might notice:

• Tender and painful lymph nodes
• Swollen lymph nodes that may be the size of a pea or kidney bean, or even larger

Depending on the cause of your swollen lymph nodes, other signs and symptoms you might have include:

• Runny nose, sore throat, fever and other indications of an upper respiratory infection
• General swelling of lymph nodes throughout your body — which may indicate an infection, such as HIV or mononucleosis, or an immune disorder, such as lupus or rheumatoid arthritis
• Swollen limb, possibly indicating lymph system blockage caused by swelling in a lymph node too far under your skin to feel
• Hardened, fixed, rapidly growing nodes, indicating a possible tumor
• Fever
• Night sweats

When to see a doctor

Some swollen lymph nodes return to normal when the underlying condition, such as a minor infection, resolves. However, see your doctor if you're concerned or if your swollen lymph nodes:

• Have appeared for no apparent reason
• Continue to enlarge or have been present for two to four weeks
• Feel hard or rubbery, or don't move when you push on them
• Are accompanied by persistent fever, night sweats or unexplained weight loss
• Are accompanied by a sore throat or by difficulty swallowing or breathing

Source: http://www.mayoclinic.com

A lymph node is a small, round or bean-shaped cluster of cells covered by a capsule of connective tissue. The cells are a combination of lymphocytes — which produce protein particles that capture invaders, such as viruses — and macrophages, which break down the captured material. Lymphocytes and macrophages filter your lymphatic fluid as it travels through your body and protect you by destroying invaders.

Lymph nodes are located in groups, and each group drains a specific area of your body. You may be more likely to notice swelling in certain areas, such as in the lymph nodes in your neck, under your chin, in your armpits and in your groin. The site of the swollen lymph nodes may help identify the underlying cause.

The most common cause of swollen lymph nodes is an infection, particularly a viral infection, such as the common cold. However, there are other types of infections, including parasitic and bacterial, and other possible causes of swollen lymph nodes. They include:

Common infections

• Strep throat
• Measles
• Ear infections
• Infected (abscessed) tooth
• Mononucleosis
• Skin or wound infections, such as cellulitis or erysipelas
• Human immunodeficiency virus (HIV) — the virus that causes AIDS

Uncommon infections

• Tuberculosis
• Certain sexually transmitted infections, such as syphilis
• Toxoplasmosis — a parasitic infection resulting from contact with the feces of an infected cat or eating undercooked meat
• Cat scratch fever — a bacterial infection from a cat scratch or bite

Immune system disorders

• Lupus — a chronic inflammatory disease that can target your joints, skin, kidneys, blood cells, heart and lungs
• Rheumatoid arthritis — a chronic inflammatory disease that targets the tissue that lines your joints (synovium)

Cancers

• Lymphoma — cancer that originates in your lymphatic system
• Leukemia — cancer of your body's blood-forming tissue, including your bone marrow and lymphatic system
• Other cancers that have spread (metastasized ) to lymph nodes

Other possible, but rare causes include certain medications, such as the anti-seizure medication phenytoin (Dilantin), and preventive medications for malaria.

Source: http://www.mayoclinic.com

To diagnose what might be causing your swollen lymph nodes, your doctor may need:

• Your medical history. In addition, your doctor will want to know when and how your swollen lymph nodes developed and if you have any other signs or symptoms.
• A physical exam. Your doctor will also want to check lymph nodes near the surface of your skin for size, tenderness, warmth and texture. The site of your swollen lymph nodes and your other signs and symptoms will offer clues to the underlying cause.
• Blood tests. Depending on what your doctor suspects is causing your swollen lymph nodes, certain blood tests may be done to confirm or exclude the suspected underlying condition. The specific tests will depend on the suspected cause, but most likely will include a complete blood count (CBC), which helps evaluate your overall health and detect a range of disorders, including infections and leukemia.
• Imaging studies. A chest X-ray or computerized tomography (CT) scan of the affected area may help determine potential sources of infection or find tumors.

• Lymph node biopsy. If your doctor can't pin down the diagnosis, it may be helpful to remove a sample from a lymph node or even an entire lymph node for microscopic examination.

  The method of biopsy may be fine-needle aspiration (FNA), which your doctor may perform during an office visit, or you may be referred to a surgeon or radiologist for this procedure. In FNA, the doctor inserts a thin, hollow needle into the lymph node and removes (aspirates) cells, which are then sent to a lab for study. Ultrasound — a noninvasive procedure that uses sound waves to create images of organs and tissues — may be used to guide the needle and ensure accuracy.

  In some cases, you may require an excisional biopsy. This type of biopsy — also called surgical biopsy — removes a portion or all of a lymph node through an incision for analysis. A surgeon performs this procedure while using local or general anesthetics.

Lymph node biopsy. If your doctor can't pin down the diagnosis, it may be helpful to remove a sample from a lymph node or even an entire lymph node for microscopic examination.

The method of biopsy may be fine-needle aspiration (FNA), which your doctor may perform during an office visit, or you may be referred to a surgeon or radiologist for this procedure. In FNA, the doctor inserts a thin, hollow needle into the lymph node and removes (aspirates) cells, which are then sent to a lab for study. Ultrasound — a noninvasive procedure that uses sound waves to create images of organs and tissues — may be used to guide the needle and ensure accuracy.

In some cases, you may require an excisional biopsy. This type of biopsy — also called surgical biopsy — removes a portion or all of a lymph node through an incision for analysis. A surgeon performs this procedure while using local or general anesthetics.

Source: http://www.mayoclinic.com

If infection is the cause of your swollen lymph nodes and isn't treated, these complications might occur:

• Abscess formation. An abscess is a localized collection of pus caused by an infection. Pus contains fluid, white blood cells, dead tissue and bacteria or other invaders. An abscess may require drainage and antibiotic treatment. An abscess may cause significant damage if it involves a vital organ.
• Bloodstream infection (bacteremia). A bacterial infection anywhere in your body can progress to sepsis, caused by an overwhelming infection of the bloodstream. Sepsis may result in organ failure and death. Treatment involves hospitalization and intravenous antibiotics.

Source: http://www.mayoclinic.com

If your swollen lymph nodes are tender or painful, you might get some relief by doing the following:

• Apply warmth. Apply a warm, wet compress, such as a washcloth dipped in hot water and wrung out, to the affected area.
• Take pain relievers. Over-the-counter pain relievers, such as aspirin, ibuprofen (Advil, Motrin IB, others) and acetaminophen (Tylenol, others), may help alleviate pain and fever. Don't give your child aspirin without consulting your doctor because of its link to Reye's syndrome in children. Reye's syndrome is a rare but serious illness that can affect the blood, liver and brain of a child or teenager recovering from a viral infection.
• Get adequate rest. You often need rest to aid your recovery from the underlying condition.

Source: http://www.mayoclinic.com