Lymph nodes are small glands that filter lymph, the clear fluid that circulates through the lymphatic system. During an infection, they accumulate bacteria or dead or diseased cells and may swell.

When a person has an infection, they may notice swollen lymph nodes in part of the body near the infection site, such as their neck, armpit, jaw, or groin.

For instance, a person with a sore throat due to COVID-19 may have swollen lymph nodes in their neck. They may also have other symptoms of an infection, such as coughing, fatigue, and fever.

Cancer that develops in or spreads to the lymph nodes may also be swollen. In this case, the reason for swelling may be a tumor.

In this article, find out more about why lymph nodes become swollen, what it might mean, and when to see a doctor.

The lymphatic system consists of channels throughout your body that are similar to blood vessels. Lymph nodes are small glands that filter lymph, the clear fluid that circulates through the lymphatic system.

Lymph nodes are located throughout the body. They can be found underneath the skin in many areas, including:

Lymph nodes store white blood cells, which are responsible for killing invading organisms.

They also act like a checkpoint. When bacteria, viruses, and abnormal or diseased cells pass through the lymph channels, the lymph nodes detect and stop them.

When faced with an infection or illness, the lymph nodes accumulate debris, such as bacteria and dead or diseased cells.

Lymphadenopathy is another name for swelling in the lymph nodes. Symptoms that may be present along with swollen lymph nodes in the neck, for instance, are:

Swollen lymph nodes in the groin may occur with a pelvic infection. They can cause pain when walking or bending.

Swollen lymph nodes are one sign that your lymphatic system is working to rid your body of infection and illness.

Infections

Lymph nodes swell when an infection occurs in the area where they’re located. For example, the lymph nodes in the neck can become swollen in response to an upper respiratory infection, such as the common cold.

Lymph nodes that swell due to an infection may be painful.

Swollen lymph nodes in the head and neck may stem from infections such as:

Sexually transmitted infections (STIs) such as syphilis or gonorrhea can bring about lymph node swelling in the groin area.

Other possible causes include:

Noninfectious causes

Serious conditions, such as immune system disorders or cancers, can cause lymph nodes throughout the body to swell.

Immune system disorders that cause the lymph nodes to swell include lupus and rheumatoid arthritis.

Any cancers that spread in the body can cause the lymph nodes to swell. When cancer from one area spreads to the lymph nodes, the survival rate decreases. Lymphoma, which is a cancer of the lymphatic system, also causes the lymph nodes to swell.

Cancers that can cause swollen lymph nodes include:

Other causes of swollen lymph nodes include, but aren’t limited to:

Swollen lymph nodes can be as small as peas or as large as cherries.

They can be painful to the touch, or they can hurt when you make certain movements.

Swollen lymph nodes under the jaw or on either side of the neck may hurt when you turn your head in a certain way or you’re chewing food. They can often be felt simply by running your hand over your neck just below your jawline. They may be tender as well.

If you’ve recently become ill or had an injury, let a doctor know. This information is vital in helping them determine the cause of your symptoms.

The doctor will also ask you about your medical history. Since certain diseases or medications can cause swollen lymph nodes, giving your medical history helps them find a diagnosis.

After you discuss the symptoms with the doctor, they’ll perform a physical examination.

This consists of:

  • checking the size of your lymph nodes
  • feeling them to see if they’re tender
  • checking the consistency, whether they are hard and firm versus soft and moveable
  • discussing whether they have changed or become larger over time

After the physical examination, blood tests may be ordered to check for certain diseases.

If necessary, the doctor may order an imaging test to further evaluate the lymph node or other areas of your body that may have caused the lymph node to swell. Common imaging tests used to check lymph nodes include:

If the above tests suggest the need for further evaluation, the doctor may order an MRI.

In certain cases, even further testing may be needed following the MRI. In this case, the doctor may order a lymph node biopsy. This is a minimally invasive test that consists of using thin, needle-like tools to remove a sample of cells from the lymph node. The cells are then sent to a laboratory where they’re tested for major diseases, such as cancer.

If necessary, the doctor may remove the entire lymph node.

Swollen lymph nodes may become smaller on their own without any treatment. In some cases, the doctor may wish to monitor them without treatment.

In the case of an infection, you may be prescribed antibiotics or antiviral medications to eliminate the condition responsible for the swollen lymph nodes. Your doctor might also recommend medications such as acetaminophen (Tylenol) and ibuprofen (Advil, Motrin) to help relieve pain and reduce inflammation.

Swollen lymph nodes caused by cancer may not shrink back to their usual size until the cancer is treated. Cancer treatment may involve removing the tumor or any affected lymph nodes. It may also involve chemotherapy to shrink the tumor.

Your doctor will discuss which treatment option is best for you.

The only way to prevent swollen lymph nodes is to prevent the conditions that may cause them. Some steps you can take are below:

  • Practice proper dental hygiene to help keep your teeth and gums healthy.
  • Wash your hands frequently.
  • Get vaccinated against conditions such as shingles, tuberculosis, and the flu.
  • Avoid sharing food, beverages, or personal items such as towels with anyone who has a contagious infection such as mono or a cold.
  • Use condoms or other barrier methods during sexual activity.
  • Ask your doctor about switching your medications if you’re having an adverse or allergic reaction.
  • Avoid feral cats or letting your pet cats play outdoors.

If you experience any of the symptoms that sometimes accompany swollen lymph nodes, or if you have painful swollen lymph nodes and no other symptoms, talk with a doctor. Lymph nodes that are swollen but not tender can be signs of a serious problem.

In some cases, the swollen lymph node will get smaller as other symptoms go away. If a lymph node is swollen and painful or if the swelling lasts more than a few days, also see a doctor.

When should you worry about a swollen lymph node?

You should seek medical advice if lymph nodes:

  • are very swollen
  • are becoming bigger
  • either are tender or are not tender
  • do not resolve within a few days
  • occur with other symptoms you have concerns about

What is the main cause of swollen lymph nodes?

Most cases of swollen lymph nodes occur alongside an infection. They are a sign that the body is fighting the infection and stopping it from causing serious harm in the body.

In rare cases, swollen lymph nodes made be a sign of cancer, including lymphoma or leukemia. These lymph nodes tend to not be tender and not associated with an obvious infection or injury.

They may also occur with autoimmune conditions, such as lupus.

Are swollen lymph nodes serious?

In most cases, swollen lymph nodes are not serious but indicate that the immune system is doing its job. However, they can indicate an infection that needs medical attention.

Persistent swelling in the lymph nodes that occurs without other signs of an infection can indicate some types of cancer.

What does a swollen lymph feel like?

You may be able to feel a swollen lymph node with your fingers, although this is not always possible, as some are quite deep in the body or do not swell enough to become noticeable.

Sometimes, there is pain with the swelling, or it may be painful, for example, to turn the head.

Swelling without pain may be a sign of a tumor. Under the arm, it may indicate that breast cancer is spreading.

Swollen lymph nodes are usually a sign of an infection somewhere in the body. You may notice swelling and tenderness, for instance, in the neck, groin, or armpits, alongside other symptoms, such as a sore throat.

Swelling in the lymph nodes can occur with some types of cancer, such as lymphoma, leukemia, and breast cancer. If you have concerns about swollen lymph nodes, it is best to seek medical help, especially if the swelling persists or if you have other worrisome symptoms.