Lymph nodes help your body fight off infections. These tiny glands work as filters and trap bacteria, viruses, and other causes of illness to prevent them from infecting other parts of your body.

Lymph nodes normally measure less than ½ inch across, which is approximately the size of a pea. They can grow significantly, sometimes getting as big as a tennis ball.

Lymph nodes in the groin are also called inguinal lymph nodes. Swollen nodes in the groin can be caused by an injury or skin infection, such as athlete’s foot. Sexually transmitted infections (STIs) and cancer can also cause swollen lymph nodes in the groin.

More often than not, swollen inguinal lymph nodes are caused by infections or injury affecting the lower body. This can include the:

  • groin
  • genitals
  • urinary tract
  • leg
  • foot

Examples of these include:

  • Athlete’s foot: a fungal infection that usually begins with a scaly rash between the toes
  • Jock itch:a fungal infection that causes a red, itchy rash in the groin area
  • Vaginal or penile yeast infection: a common infection caused by an overgrowth of the fungus Candida
  • Urinary tract infection (UTI): a common infection that can affect any part of the urinary tract
  • Cellulitis: a common and potentially serious skin infection that most often affects the lower legs, and cause redness and swelling
  • Balanitis: a skin irritation on the foreskin and head of the penis that is more common in those who are uncircumcised
  • Prostatitis: a swelling of the prostate gland that can be caused by a bacterial infection or injury
  • Cystitis: inflammation of the bladder most often caused by a UTI, but can also be caused by certain medications or irritating hygiene products
  • Genital herpes: an STI that often begins with flu-like symptoms and swollen lymph nodes in the groin, before an outbreak of genital blisters
  • Gonorrhea: a very common STI that often causes no symptoms, but can cause discharge and painful urination
  • Syphilis: a serious STI that begins with a sore called a chancre and develops in stages, leading to serious complications if not treated
  • HIV:a virus that affects the immune system and begins with flu-like symptoms and swollen lymph nodes

In rare cases, swollen lymph nodes in the groin could be due to cancer. Cancer in the back, pelvis, and lower extremities can spread to the inguinal lymph nodes. Some of these types of cancer include:

Swollen lymph nodes can also be caused by other cancers, such as lymphoma and leukemia. These types of cancers are more likely to cause multiple areas of nodes to swell.

Immunodeficiency disorders and infections, such as mononucleosis and chickenpox can also cause it.

Normal lymph nodes are small, painless, and move under the skin when pushed.

Most of the time, lymph nodes will swell in one area, close to the site of the injury or infection. When more than one area of nodes swells, it’s called generalized lymphadenopathy.

Certain infections and cancers are more likely to cause multiple areas of lymph nodes to swell, including lymphoma, leukemia, and HIV. Measles, conditions that affect the immune system, and certain medications can also cause generalized lymphadenopathy.

According to Cleveland Clinic, a lymph node larger than 0.4 inches, or 1 centimeter, in diameter is considered abnormal.

Swollen lymph nodes in the groin may be painful to the touch and the skin over them may look red and inflamed, depending on the cause.

If your swollen nodes are due to a lower body infection or injury, your other symptoms may include:

Other symptoms are more common when swollen lymph nodes are caused by cancer. These include:

To diagnose the cause of swollen lymph nodes in the groin, your doctor will begin with your medical and sexual history. They’ll ask about your symptoms, including how long your lymph nodes have been swollen.

Since certain medications can cause lymphadenopathy, the doctor will also want to know what medications you are taking.

Your doctor may also need to do additional testing, which may include:

  • Physical exam. Your doctor will examine your swollen lymph nodes for size, consistency, pain, and warmth. They’ll also check for other lymphadenopathy and signs of infection and illness, including STIs.
  • Urinalysis. You may be asked to provide a sample of your urine to check for signs of a UTI or other infection, including STIs.
  • Pap test. A Pap test checks the cervix for abnormal cells and cervical cancer. An HPV test may be performed as well. HPV has been linked to cancer of the:
    • vulva
    • vagina
    • cervix
    • anus
  • STI testing. Along with cervical swabs and urine and blood samples, urethral swabs and other STI tests may be performed if an STI is suspected.
  • Blood tests. Certain blood tests can help diagnose an underlying condition, including infections and leukemia. The blood tests ordered will depend on what your doctor suspects is causing your swollen nodes. This may include a complete blood count (CBC), blood culture, and HIV tests.
  • Imaging tests. Your doctor may order one or more types of imaging tests to help determine possible sources of infection or locate tumors. Imaging tests used may include an ultrasound of your abdomen, pelvis, and groin, or a CT scan of the affected area.
  • Lymph node biopsy. If other tests don’t provide a diagnosis or cancer is suspected, your doctor may recommend a biopsy. A sample from a lymph node or an entire lymph node may be removed. The doctor will usually choose to biopsy the largest lymph node.

Swollen lymph nodes in the groin are a symptom, not a condition. Treatment depends on what’s causing your nodes to swell.

If an infection is the cause, treatment depends on the type of infection and may include a topical treatment, oral treatment, or a combination of both.

Treatments include:

If cancer is causing your swollen lymph nodes, treatment depends on the type of cancer, the stage, and your age and overall health. Options may include:

Swollen lymph nodes usually return to normal when the underlying condition gets better. For instance, if you have a minor skin infection, such as athlete’s foot, your lymph nodes should go back to their normal size once you’ve treated the infection.

Any lump in your groin should be evaluated by a doctor. See your doctor if:

  • the swelling appeared for no obvious reason, such as a skin infection or injury
  • the swelling is present for more than two weeks or continue to enlarge
  • your lymph nodes feel hard or don’t move when you push on them
  • the swelling is accompanied by persistent fever, unexplained weight loss, or night sweats
  • you’ve been exposed to an STI

Most swollen lymph nodes in the groin are caused by a lower body infection or injury, but it could be something more serious. Talk with your doctor, especially if you have other symptoms.