Swollen lymph nodes in the groin: STI or not?

Key takeaways

• Swollen lymph nodes in the groin are most often caused by a minor skin infection on the leg or foot, shaving irritation, or a small cut or injury nearby, not an STI.
• Herpes, syphilis, HIV seroconversion and, less commonly, LGV or chancroid can all cause groin swelling as part of a wider picture of symptoms.
• A lump that persists for more than two to three weeks, feels hard or fixed rather than soft and mobile, keeps growing, or comes with night sweats or unexplained weight loss needs a GP assessment.
• Testing for the STI causes of groin swelling, including herpes, syphilis and HIV, is available at Sexual Health Clinic London, and a combined screen such as our packages covers several of these in one visit.
• Lymph nodes are part of the immune system and commonly swell in response to almost any nearby infection, so a swollen node on its own is not proof of anything specific.
• If a lump is persistent or concerning rather than a straightforward suspected infection, a GP review is the right next step.

A swollen lymph node in the groin usually means your immune system is responding to an infection somewhere in the leg, foot or genital area, and in most cases that infection is nothing to do with an STI. Because herpes, syphilis and HIV can all cause the same swelling, though, it is worth having it checked if it appears alongside other symptoms or does not settle. Our screening packages cover the STI causes in one visit.

What are lymph nodes, and why do they swell in the groin?

Lymph nodes are small, bean-shaped glands that filter fluid as part of the immune system, and the ones in the groin drain the legs, feet and genital area. They swell when the immune system is actively responding to an infection or irritation nearby, which is a normal and usually temporary reaction rather than a disease in itself. Because the groin nodes drain such a wide area, almost any infection on the leg, foot or genitals can cause them to enlarge.

What non-STI causes are most common?

The most common causes are ordinary and local: a skin infection on the leg or foot, such as from a cut, insect bite or athlete's foot, irritation or a small infected hair follicle from shaving or waxing the groin area, or a minor injury or graze nearby. These typically cause a soft, mobile, mildly tender lump that settles within one to two weeks as the underlying skin issue heals. Viral illnesses unrelated to sexual health, such as a common cold or flu, can also cause mild, widespread lymph node swelling, including in the groin. Not every groin lump is a lymph node: a hernia or a cyst can also cause a lump there, which is another reason a lump that persists needs examining.

Which STIs can cause swollen groin lymph nodes?

Several STIs can cause groin swelling, usually alongside other symptoms rather than as the only sign.

A brief comparison of the sexually transmitted causes of groin lymph node swelling and what else tends to go with them.

Herpes can cause tender groin swelling alongside its typical blisters or sores, particularly during a first outbreak. Syphilis in its early stage classically causes a painless sore along with swollen nodes near the site of infection. HIV seroconversion, the body's initial reaction to the virus, often produces a short flu-like illness with fever, sore throat, rash and swollen glands two to six weeks after exposure, though many people have no symptoms at all. Lymphogranuloma venereum (LGV) and chancroid are two less common infections that can cause more prominent groin swelling alongside genital ulcers; both are uncommon in the UK.

When does a groin lump need a GP rather than an STI test?

A lump needs a GP assessment if it has persisted for more than two to three weeks, feels hard or fixed in place rather than soft and mobile, is steadily growing, or is accompanied by night sweats or unexplained weight loss. These features do not necessarily mean anything serious, but they fall outside what a straightforward infection-related swelling usually looks like, so they warrant a proper clinical assessment rather than an STI test alone. If this describes your lump, the private GP service at Medical Express Clinic, where a consultation is £150, can arrange the right examination and, if needed, further investigation.

Which tests should I book?

If the swelling has appeared alongside a sore, blister, rash or recent unprotected sex, the most useful starting point is testing for the infections most likely to cause it. Herpes is confirmed with a swab of an active sore, or a blood test if there is no visible sore. Syphilis and HIV are both confirmed with a blood test. If you are not sure which infection is most likely, or want a broader check in one visit, a combined screening package covers several of these together. Our guide to private STI testing in London explains how a confidential visit works.

How testing works at our Harley Street clinic

At Sexual Health Clinic London, the Bronze package at £250 covers chlamydia, gonorrhoea, HIV and syphilis in one visit, with the HIV test priced individually at £75 plus a £50 blood draw (£125 total) and the syphilis test at £85 plus the £50 blood draw (£135 total) if you prefer to test for either on its own. The herpes test is a PCR swab of an active sore (£120.63) or a blood test (£103.75), with results in 2 to 3 days. If you want faster results, FAST Screen Simple (£350) returns HIV, syphilis, chlamydia and gonorrhoea results in 6 hours. Walk-in appointments are available seven days a week at 117a Harley Street, and results are given confidentially.

Walk in or book an STI screening package at 117a Harley Street: Bronze £250, FAST Screen results in 6 hours.

References

• Swollen lymph glands, NHS
• Genital herpes, NHS
• Syphilis, NHS
• HIV and AIDS, NHS
• Lymphogranuloma venereum, British Association for Sexual Health and HIV (BASHH)