What causes enlarged lymph nodes in the groin?

September 27, 2025 •

5 min read

Swollen lymph nodes are a common clinical sign, and according to the National Institutes of Health (NIH), they often point to the body's immune system fighting an infection. This is especially true for the inguinal lymph nodes located in the groin, as their enlargement, or lymphadenopathy, can signal a local infection or inflammation. Understanding what causes enlarged lymph nodes in the groin is a vital step toward recognizing when to seek medical advice.

Quick Summary

Enlarged groin lymph nodes are typically caused by infections affecting the lower body, such as cellulitis, STIs, or fungal infections, but can also result from autoimmune diseases or, in rare cases, certain cancers. They swell as a normal immune response, trapping bacteria, viruses, and other harmful substances. Persistent swelling warrants a medical evaluation to determine the underlying cause and appropriate treatment.

Key Points

Immune Response: Enlarged lymph nodes in the groin, known as inguinal lymphadenopathy, are a primary sign that your immune system is actively fighting an infection or inflammation in the lower body or genital area.
Common Causes: The most frequent causes are local infections like cellulitis on the leg or foot, as well as sexually transmitted infections (STIs) such as syphilis and genital herpes.
Fungal Infections: Fungal issues like athlete's foot and jock itch can also trigger lymph node swelling in the groin area.
When to See a Doctor: Seek medical attention if the swelling is unexplained, persists for more than 2-4 weeks, feels hard and immobile, or is accompanied by other serious symptoms like fever, night sweats, or weight loss.
Diagnostic Process: A healthcare provider will likely perform a physical exam and may order tests such as blood work, imaging scans (ultrasound, CT), or a biopsy to determine the cause.
Cancer is a Possibility: Though rare, enlarged groin lymph nodes can indicate cancer, such as lymphoma or the metastasis of a cancer from the pelvis or lower extremities.
Treatment Depends on Cause: The treatment for enlarged lymph nodes is directed at the underlying cause, whether that is antibiotics for a bacterial infection or specific therapies for an autoimmune disorder or cancer.

Understanding the Lymphatic System

Lymph nodes are a critical component of your immune system, acting as filters to trap viruses, bacteria, and other foreign substances. Located throughout the body, including the neck, armpits, and groin, these small, bean-shaped glands play a crucial role in fighting off disease. The inguinal lymph nodes in the groin specifically filter lymphatic fluid from the genitals, legs, and feet, so an enlargement in this area often points to a problem within those regions.

When your body detects an infection or inflammation, the immune cells within the lymph nodes multiply to fight the invading pathogens. This cellular activity causes the nodes to swell, often becoming tender and painful to the touch. Once the infection resolves, the swelling typically subsides. However, persistent or unexplained enlargement requires medical attention.

Common Infectious Causes

Infections are the most frequent reason for swollen lymph nodes in the groin. The body's immune response to a localized infection in the lower extremities or genital region is often a primary driver of inguinal lymphadenopathy.

Skin and Soft Tissue Infections

Cellulitis: This common bacterial skin infection can occur anywhere on the body, but if it develops on the legs or feet, it can cause the groin lymph nodes to swell. Symptoms include a red, swollen, warm, and tender area of skin.
Foot Injuries and Infections: Simple cuts, blisters, or infected wounds on the feet or lower legs can trigger a lymph node response in the groin. Athlete's foot, a fungal infection, can also lead to swelling.
Folliculitis and Ingrown Hairs: Infections of hair follicles or inflamed ingrown hairs in the pubic or inner thigh area can cause a localized reaction in the nearest lymph nodes.

Sexually Transmitted Infections (STIs)

Several STIs are well-known causes of enlarged groin lymph nodes, which swell in response to the infection in the genital area. Regular screening is important, as many STIs have few or no other symptoms.

Syphilis and Gonorrhea: These bacterial infections can lead to generalized or localized lymphadenopathy.
Genital Herpes: This viral infection is characterized by painful blisters and can cause the lymph nodes to swell during outbreaks.
Chancroid and Lymphogranuloma Venereum (LGV): These less common bacterial STIs can cause significant swelling and tenderness of the inguinal lymph nodes.

Fungal and Other Infections

Jock Itch (Tinea Cruris): A fungal infection of the groin and inner thighs, jock itch can cause a red, itchy rash and lead to swollen groin lymph nodes as part of the body's immune response.
Yeast Infections: Both vaginal and penile yeast infections, caused by an overgrowth of Candida, can trigger a local inflammatory response that includes lymph node swelling.
Cat Scratch Disease: This bacterial infection, transmitted through a cat's scratch or bite, can cause swelling in the lymph nodes near the site of the injury.

Systemic and Autoimmune Diseases

Sometimes, enlarged lymph nodes in the groin are part of a more widespread issue affecting the whole body, rather than a localized infection.

Lupus and Rheumatoid Arthritis: These autoimmune diseases can cause generalized lymphadenopathy, where lymph nodes swell throughout the body, including the groin.
Infectious Mononucleosis (Mono): This viral infection is known for causing widespread swollen lymph nodes, especially in the neck, but it can affect nodes in the groin as well.
HIV: Early HIV infection can cause generalized lymphadenopathy as the virus attacks the immune system.

Malignancy (Cancer) as a Cause

While cancer is a less common cause of enlarged lymph nodes than infection, it is a serious possibility, especially if the swelling is persistent and other symptoms are present. Cancerous lymph nodes often differ from those caused by infection.

Lymphoma: This cancer of the lymphatic system can cause lymph nodes to become enlarged, hard, and painless.
Metastasis from Other Cancers: Cancer cells from other parts of the body can travel through the lymphatic system and get trapped in the groin nodes. This is common with cancers of the vulva, penis, anus, and lower extremities.
Melanoma: This type of skin cancer can spread to regional lymph nodes, including those in the groin.

Differential Diagnosis: Normal vs. Abnormal

Distinguishing between a harmless, reactive lymph node and a more serious issue is key. A normal inguinal lymph node is typically small and oval-shaped. An abnormal node may exhibit certain characteristics that warrant further investigation.


Feature	Normal Lymph Node	Abnormal Lymph Node
Size	Up to 1.5 cm (about 0.6 inches)	Larger than 1.5 cm, or continuously growing
Shape	Ovoid or bean-shaped	More rounded
Consistency	Soft and mobile, feels rubbery like the tip of your nose	Hard, firm, and fixed in place
Tenderness	Often tender and painful with infection	May be painless, especially with malignancy
Duration	Usually resolves within a couple of weeks	Persists for more than 2-4 weeks
Associated Symptoms	Fever, rash, other signs of localized infection	Persistent fever, night sweats, unexplained weight loss

When to See a Doctor

While most swollen lymph nodes resolve on their own, certain signs indicate the need for a professional medical evaluation. You should consult a healthcare provider if:

The swelling appeared without an obvious cause, such as a local infection or injury.
The lymph nodes have been swollen for more than two weeks or continue to enlarge.
The nodes feel hard, fixed, or are not tender to the touch.
You experience additional symptoms like persistent fever, night sweats, or unexplained weight loss.
You have been exposed to a sexually transmitted infection.

Diagnostic and Treatment Approaches

Diagnosing the cause of enlarged groin lymph nodes involves a thorough medical history and physical examination. A healthcare provider may also order several tests to pinpoint the problem.

Blood Tests: To check for signs of systemic infections, inflammation, or certain types of cancer.
Imaging Tests: An ultrasound or CT scan may be used to examine the size and characteristics of the lymph nodes and surrounding structures.
Lymph Node Biopsy: A tissue sample from the enlarged node may be taken and examined under a microscope to confirm or rule out cancer.

Treatment directly depends on the underlying cause. Infections may be treated with antibiotics or antifungal medications, while autoimmune conditions may require immune-regulating therapy. For cancer, treatment plans can include surgery, chemotherapy, or radiation therapy.

Conclusion

Enlarged lymph nodes in the groin are a common occurrence, usually indicating a normal immune response to a local infection. However, understanding the less common, yet more serious, causes is crucial for proactive health management. Paying attention to the characteristics of the swelling—such as its size, consistency, and duration—along with any accompanying symptoms, can help you decide when to seek medical advice. As with any health concern, a prompt and accurate diagnosis from a healthcare professional is the best path to appropriate treatment and peace of mind. For more information on health, consider visiting a reliable source like the Cleveland Clinic.

Frequently Asked Questions

While most enlarged lymph nodes are benign, a serious cause might be indicated if the node is hard, fixed, and painless, or if the swelling persists for more than two to four weeks. Accompanying symptoms like unexplained weight loss, night sweats, or persistent fever also warrant immediate medical evaluation.

Yes, a minor injury or infection on the leg, foot, or in the genital area can cause the nearby lymph nodes in the groin to swell. This is a normal part of the immune system's response to filter out pathogens.

An enlarged lymph node feels like a firm, roundish lump, while a hernia often presents as a softer, larger bulge in the groin that may become more prominent with coughing or straining. Unlike lymph nodes, hernias are caused by tissue pushing through a weak spot in the abdominal wall.

If caused by an infection, the swelling of a lymph node should typically begin to decrease within a few days to a couple of weeks after the infection has resolved. If swelling persists beyond this timeframe, it should be medically evaluated.

Yes, minor nicks, cuts, or infected hair follicles resulting from shaving can sometimes cause a localized skin infection. The lymph nodes in the groin may swell in response as they work to clear the infection.

Yes, it is possible for a lymph node to remain enlarged for some time, even after the initial infection has resolved. The body takes time to clear the immune cells that caused the swelling. However, if it remains swollen for an extended period, it's best to consult a doctor.

While painful lymph nodes often indicate infection, painless swelling can sometimes be associated with more serious conditions, including cancer. If an enlarged lymph node in your groin is not painful, especially if it is hard or fixed in place, you should see a healthcare provider for a thorough examination.