What can trigger swollen lymph nodes?

September 24, 2025 •

4 min read

Approximately 70% of all lymph nodes are located in the neck, armpits, and groin, where they can often be felt when they swell. It is essential to understand what can trigger swollen lymph nodes to properly identify potential health issues and decide when to seek medical advice.

Quick Summary

Swollen lymph nodes are most commonly caused by infections, as the immune system's lymphatic glands work overtime to fight off foreign invaders like bacteria and viruses. Less frequently, they can be triggered by inflammatory conditions, autoimmune disorders, and, in rare cases, certain cancers. This guide details the various reasons and circumstances behind the condition.

Key Points

Infections are the leading cause: The immune system's response to viral and bacterial infections, such as the common cold, flu, or strep throat, is the most frequent reason for swelling.
Location indicates the problem: The area of the swollen nodes often pinpoints the site of the infection, such as neck nodes for throat infections or groin nodes for lower body issues.
Less common triggers exist: Beyond infections, autoimmune diseases like lupus or rheumatoid arthritis, and certain medications, can also cause swollen lymph nodes.
Cancer is a possibility: Though rare, persistent, painless, and hard lymph node swelling can be a sign of cancer, including lymphoma or metastatic cancer.
Know when to seek medical help: If swelling lasts more than two weeks, is accompanied by night sweats or weight loss, or feels hard and fixed, it's time to see a doctor.
Distinguish between causes: Knowing if the nodes are tender, movable, and rapidly developed can help differentiate between an infection and a more serious condition.

The Role of Lymph Nodes in Your Body

Your lymph nodes, also known as lymph glands, are small, bean-shaped structures that play a crucial role in your body's immune system. They filter the lymphatic fluid and store white blood cells, which are vital for fighting off infections. When these nodes detect a threat, they produce more white blood cells, which causes them to enlarge or swell. Understanding their function is the first step in comprehending what can trigger swollen lymph nodes.

Common Infectious Causes

The vast majority of swollen lymph node cases are due to infections. Your body's response to these infections is a clear sign that your immune system is hard at work. The location of the swollen nodes often provides a clue as to the site of the infection.

Viral Infections

The Common Cold and Flu: Upper respiratory tract infections are a very frequent cause. Nodes in the neck may swell as they combat the viruses responsible.
Mononucleosis (Mono): This virus, often called the "kissing disease," can cause significantly swollen lymph nodes, especially in the neck and armpit area, alongside other symptoms like fatigue and a sore throat.
HIV/AIDS: Swollen lymph nodes are a common early symptom and can reappear in later stages as the virus weakens the immune system.
Measles and Chickenpox: These childhood illnesses also trigger an immune response that includes enlarged lymph nodes.

Bacterial Infections

Strep Throat: An infection of the throat caused by Streptococcus bacteria can lead to tender, swollen nodes in the neck.
Skin Infections: Bacterial infections like cellulitis or an abscess near a lymph node group will often cause the nearby nodes to swell.
Tuberculosis: While less common in many developed countries, this bacterial infection can cause lymph nodes to swell, especially in the neck and chest.
Cat Scratch Fever: Caused by Bartonella henselae, this infection from a scratch or bite from a cat can cause lymph node swelling near the wound site.

Non-Infectious Triggers

Beyond infections, several other conditions can cause lymph nodes to swell. These are often related to systemic inflammatory or autoimmune responses.

Inflammatory Conditions

Rheumatoid Arthritis: This autoimmune disease, which causes chronic joint inflammation, can also trigger a generalized swelling of the lymph nodes throughout the body.
Lupus (Systemic Lupus Erythematosus): A systemic autoimmune disease that can affect many parts of the body, including the lymph nodes.
Sarcoidosis: This condition results in the growth of tiny collections of inflammatory cells (granulomas) in different parts of the body, with lymph nodes being a common site.

Cancer and Malignancy

While less common, cancer can be a cause of swollen lymph nodes. This is often a significant concern for those who find persistent, hard, or painless swelling.

Lymphoma: A type of cancer that begins in the lymphatic system itself. Swollen lymph nodes are a primary symptom.
Leukemia: A cancer of the blood and bone marrow, which can cause lymph nodes to swell throughout the body.
Metastatic Cancer: When cancer from another part of the body, such as the breast, lung, or stomach, spreads to the lymph nodes. The nodes act as a filtering system, and when they trap cancerous cells, they can swell.

Other Potential Causes

Medications: Certain drugs, such as some anti-seizure medications and those used for preventing malaria, have been linked to lymph node swelling.
Reactions to Vaccinations: In some cases, a recent vaccination can cause the lymph nodes near the injection site to swell temporarily.

Differentiating Causes: Infection vs. Cancer

It is important to know the typical characteristics that can help differentiate between common causes. However, a medical professional is always required for a definitive diagnosis.


Feature	Typically Associated with Infection	Typically Associated with Cancer
Onset	Often rapid, appearing with other illness symptoms.	Usually gradual, developing slowly over weeks or months.
Tenderness	Often tender or painful to the touch.	Generally painless or non-tender.
Texture	Soft and movable.	Hard, rubbery, or fixed to surrounding tissue.
Size	Tends to fluctuate with the severity of the illness.	Often progressively grows larger and does not subside.
Systemic Symptoms	May be accompanied by fever, sore throat, or other illness-specific symptoms.	Can be associated with unexplained weight loss, night sweats, or fatigue.

When to See a Doctor

While most cases of swollen lymph nodes resolve on their own, certain red flags should prompt a visit to a healthcare provider. You should seek medical attention if:

The swelling has lasted for more than two weeks.
The lymph nodes feel hard, fixed, or rubbery.
The swelling is accompanied by persistent fever, night sweats, or unexplained weight loss.
The swelling is accompanied by a sore throat that makes it difficult to swallow or breathe.
You have a combination of swollen lymph nodes and other symptoms that concern you.

It is always better to be cautious and seek professional advice when in doubt. The lymphatic system is a complex and vital part of your body's defense, and any persistent changes should be evaluated.

Conclusion

Infections are the most common reason for swelling, serving as a sign that your body's immune system is actively fighting off an intruder. However, there are numerous other, less common, causes, from autoimmune disorders to cancer. Understanding what can trigger swollen lymph nodes is key to a proactive approach to your health. By paying attention to associated symptoms and the characteristics of the swelling, you can make an informed decision on when to consult a healthcare professional for guidance. For more detailed information on the function of lymph nodes, you can visit the Cleveland Clinic website.

Frequently Asked Questions

The most common reason for swollen lymph nodes is an infection, whether viral (like a cold) or bacterial (like strep throat). The swelling is a sign that your immune system is creating more white blood cells to fight off the infection.

You should be concerned and see a doctor if your swollen lymph nodes are hard, feel fixed or attached to the skin, persist for more than two weeks, are accompanied by night sweats or unexplained weight loss, or appear without any other signs of infection.

While stress itself does not directly cause swollen lymph nodes, it can weaken your immune system, making you more susceptible to infections that could then cause the nodes to swell. There is no direct link between psychological stress and swelling.

Yes, severe allergies can sometimes cause lymph nodes to swell. In a severe allergic reaction, the immune system overreacts, which can lead to inflammation and swelling of the nodes, particularly in the neck.

Yes, it is possible for a vaccination to trigger temporary swelling of the lymph nodes near the injection site. This is a normal immune response to the vaccine and typically resolves on its own within a few days or weeks.

An infected lymph node is often tender, soft, and moves easily under the skin, and typically arises quickly alongside other illness symptoms. A cancerous lymph node is generally painless, hard, and fixed in place, and often grows slowly over time without other infection signs. A medical diagnosis is required for confirmation.

The time it takes for swollen lymph nodes to return to normal depends on the underlying cause. For a simple infection like a cold, they may go down within a week or two. For more persistent issues, they may remain enlarged longer. If they don't subside within two weeks, seek medical advice.

Yes, a dental infection or abscess can easily trigger swollen lymph nodes in the neck or under the jaw. The body sends immune cells to the affected area, causing the nearby nodes to swell in response to the bacterial invasion.