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. The ones in the groin drain the legs, feet and genital area. They swell when the immune system is busy with an infection or irritation nearby. That's a normal and usually temporary reaction, not a disease in itself. Because they drain such a wide area, almost any infection on the leg, foot or genitals can make them enlarge. A swollen node on its own doesn't point to any one cause.
What non-STI causes are most common?
The most common causes are ordinary and local. A skin infection on the leg or foot, from a cut, insect bite or athlete's foot, is a frequent one. So is irritation or a small infected hair follicle after shaving or waxing the groin, 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 skin heals.
Viral illnesses unrelated to sexual health, such as a common cold or flu, can also cause mild swelling of lymph nodes across the body, including the groin. And not every groin lump is a lymph node: a hernia or a cyst can cause one too, which is another reason a lump that persists is worth 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. Early syphilis classically causes a painless sore, with swollen nodes near the site of infection. HIV seroconversion is the body's first reaction to the virus. Two to six weeks after exposure, it often brings a short flu-like illness with fever, sore throat, rash and swollen glands. Many people have no symptoms at all. Lymphogranuloma venereum (LGV) and chancroid can cause more prominent groin swelling alongside genital ulcers, and both are uncommon in the UK.
When is it worth seeing a GP about a groin lump?
See a GP if the lump has lasted more than two to three weeks, or feels hard or fixed in place rather than soft and mobile. The same goes for a lump that keeps growing, or comes with night sweats or unexplained weight loss. These features don't necessarily mean anything serious. They're simply outside the usual picture of a swelling caused by infection, so a proper clinical assessment makes sense. The private GP service at Medical Express Clinic can arrange the right examination and any further investigation, and a consultation there is £150.
Which tests should I book?
If the swelling has appeared alongside a sore, blister or rash, or after recent unprotected sex, start by testing for the infections most likely to cause it.
- Herpes is confirmed with a PCR swab of an active sore (£120.63), or a blood test if there's no visible sore (£103.75). Results come back within 3 working days.
- Syphilis is confirmed with a blood test: £85 plus a £50 blood draw, £135 in total.
- HIV is also a blood test: £75 plus the £50 blood draw, £125 in total.
If you're not sure which infection is most likely, or you'd like a broader check, the Bronze package covers chlamydia, gonorrhoea, HIV and syphilis in one visit for £250. Results for blood tests come back in about 24 hours, and urine and swab results within 3 working days.
How testing works at our Harley Street clinic
If you'd like answers the same day, FAST Screen Simple (£350) covers HIV, syphilis, chlamydia and gonorrhoea, and FAST Screen Complex (£450) adds hepatitis B and C. Both return all results in 6 hours. Walk-in appointments are available seven days a week at 117a Harley Street, and results are given confidentially. You can read how private STI testing in London works before you come.
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)
