What causes swollen lymph nodes

What are Lymph Nodes?

Lymph nodes are small, bean-shaped glands found throughout your body. They are a crucial part of your immune system, acting as filters for your lymphatic fluid, which circulates throughout the body. This fluid carries waste products, dead cells, and infectious agents. Within the lymph nodes, specialized white blood cells called lymphocytes and macrophages trap and destroy these harmful substances, preventing them from spreading and causing illness. You have hundreds of lymph nodes located in clusters in areas like your neck, armpits, groin, abdomen, and chest.

What Does it Mean for Lymph Nodes to Be Swollen?

When your body is fighting off an infection or dealing with inflammation, the lymph nodes in the affected area can become enlarged or swollen. This swelling occurs because the lymph nodes are producing more white blood cells to combat the threat. The lymph nodes may feel tender or painful to the touch, and the swelling can range from the size of a pea to a grape or even larger. While swollen lymph nodes are often a sign that your immune system is working effectively, persistent or unexplained swelling warrants medical attention.

Common Causes of Swollen Lymph Nodes

Infections (The Most Frequent Cause)

The overwhelming majority of swollen lymph nodes are a direct result of your body fighting off an infection. These infections can be:

• Viral Infections: Many common viral illnesses can cause lymph nodes to swell. These include:
  • The common cold
  • Influenza (flu)
  • Mononucleosis (mono), caused by the Epstein-Barr virus
  • Measles
  • HIV
  • Herpes
  • COVID-19
• Bacterial Infections: Several types of bacterial infections can trigger lymph node swelling, such as:
  • Strep throat
  • Ear infections
  • Dental abscesses or tooth infections
  • Skin infections (like cellulitis or impetigo)
  • Tuberculosis
  • Lyme disease
• Other Infections: Less common infections like certain fungal or parasitic infections can also lead to swollen lymph nodes.

Inflammatory Conditions and Autoimmune Diseases

Sometimes, the immune system can mistakenly attack the body's own tissues, leading to chronic inflammation. In these cases, lymph nodes may swell as part of the body's generalized inflammatory response. Conditions that can cause swollen lymph nodes include:

• Rheumatoid arthritis
• Lupus (systemic lupus erythematosus)
• Sarcoidosis

Cancers

While less common than infections, swollen lymph nodes can sometimes be an indicator of cancer. This can occur in two main ways:

• Lymphoma: This is a cancer that originates in the lymphatic system itself. Lymphoma can cause lymph nodes to become significantly enlarged and often painless.
• Leukemia: These are cancers of the blood-forming tissues, including bone marrow and the lymphatic system. Swollen lymph nodes can be a symptom of leukemia.
• Metastatic Cancer: Cancer that starts in another part of the body can spread (metastasize) to the lymph nodes. For example, breast cancer can spread to the lymph nodes in the armpit, or head and neck cancers can spread to lymph nodes in the neck. The cancer cells invade the lymph nodes, causing them to swell.

Other Less Common Causes

A variety of other factors can also contribute to swollen lymph nodes, though they are less frequent:

• Reactions to Medications: Certain drugs, particularly some anti-seizure medications or antibiotics, can cause a hypersensitivity reaction that leads to swollen lymph nodes.
• Vaccinations: It's not uncommon for lymph nodes near the site of a recent vaccination to swell temporarily as the immune system responds to the vaccine.
• Injury or Trauma: Localized swelling near an injury can sometimes involve the lymph nodes.

When to See a Doctor

While swollen lymph nodes are often benign and resolve on their own, it's important to seek medical advice if you experience:

• Lymph nodes that are significantly swollen (larger than a grape)
• Swollen lymph nodes that are hard, fixed (don't move when you push them), or painless
• Swelling that persists for more than two weeks
• Swelling accompanied by persistent fever, night sweats, or unexplained weight loss
• Swelling in the collarbone area

A healthcare professional can help determine the underlying cause of your swollen lymph nodes through a physical examination, medical history, and potentially further diagnostic tests like blood work or imaging.