Syphilis: symptoms, testing and treatment explained
Quick answer
Syphilis is a bacterial STI that often causes no symptoms, or a painless sore, rash or swollen glands that can come and go over time. It's diagnosed with a blood test or a swab from a sore, and early treatment with antibiotics usually clears the infection. Testing and treatment are free and confidential on the NHS.
What syphilis is and how it's caught
Syphilis is a bacterial sexually transmitted infection caused by Treponema pallidum. It's passed on through vaginal, anal or oral sex without a condom, and through skin-to-skin contact with a syphilis sore, so a barrier method doesn't fully rule out the risk if a sore is present somewhere it doesn't cover. It can also pass from a pregnant woman to her baby.
Rates of syphilis have been rising across the UK in recent years, which is part of why sexual health services encourage regular testing rather than waiting for symptoms, many people with syphilis have no symptoms at all, especially in the early stages.
Anyone who is sexually active can catch syphilis, it isn't linked to any particular group, and it's entirely possible to pick it up from a single sexual contact. Because it's caused by bacteria rather than a virus, it behaves quite differently to infections like herpes: once treated properly, it doesn't stay dormant in the body waiting to reactivate. That's also why an accurate, correctly timed test matters so much, it's the main way syphilis gets found before it can cause lasting harm.
Symptoms by stage
Syphilis moves through stages, and what you notice (if anything) depends on which stage you're in. Symptoms usually start two to three weeks after contact, though this can range from as little as ten days to as long as three months.
| Stage | Typical timing | What you might notice |
|---|---|---|
| Primary | 2 to 3 weeks after contact | A firm, usually painless sore (chancre) where the bacteria entered the body, often on the genitals, anus or mouth |
| Secondary | A few weeks after the sore heals | A rash (often on the palms or soles), flu-like tiredness, swollen glands, or patchy hair loss |
| Latent | Can last for years | No symptoms at all, but the infection is still present and detectable on a blood test |
| Tertiary | Years later, if untreated | Rare today because testing catches most cases earlier, but can cause serious damage to the heart, brain or nerves |
The sore in the primary stage often heals on its own within a few weeks, which can wrongly feel reassuring: the infection hasn't gone, it has simply moved into its next stage. This is one of the reasons syphilis is sometimes called a great mimicker, its signs can look like other conditions or disappear on their own, so a test is the only reliable way to know.
How syphilis is diagnosed
Syphilis is usually diagnosed with a blood test, which looks for antibodies your body has made in response to the infection. If you have a visible sore, a swab taken directly from it can sometimes give a faster answer. Because antibodies take time to develop, testing too soon after a specific exposure can miss an early infection, most services recommend waiting around six weeks, with a follow-up test at twelve weeks if the first result is negative and the exposure was recent.
Testing is straightforward and confidential, whether done at a sexual health clinic, through a GP, or with a home self-sampling kit that you post to a lab. If you're unsure when to test or which option suits you, a private consultation can help you plan the right timing rather than testing blind.
A full sexual health screen usually checks for several infections at once rather than syphilis alone, since the same exposure that puts you at risk of one STI often puts you at risk of others, and symptoms can overlap. If a result comes back positive, a clinician will normally want a follow-up conversation to confirm the stage of infection and agree the right treatment plan, rather than relying on a single blood result in isolation.
How syphilis is treated
Early-stage syphilis is normally treated with a single antibiotic injection, and later stages may need a short course of three weekly injections instead. Both are usually given at a sexual health clinic, where staff are experienced in the specific dose and follow-up schedule needed. People with a penicillin allergy can usually be offered an alternative antibiotic, so it's worth mentioning any allergies when you book.
After treatment, follow-up blood tests, typically at six and twelve months, confirm your antibody levels have fallen as expected. It's important to avoid sex until you and any partners have finished treatment and been told it's safe, to avoid passing the infection back and forth.
In the first day or so after the injection, some people notice a short-lived flu-like reaction, sometimes with a mild fever, as the body responds to the treatment. This usually settles on its own within twenty-four hours and is a normal part of the process rather than a sign anything has gone wrong, though a clinician can advise on managing it if it feels uncomfortable.
Telling partners and getting retested
If you're diagnosed with syphilis, sexual health services will usually ask about recent partners so they can be offered testing too, this is called partner notification, and it can be done anonymously if you'd prefer not to contact someone yourself. It protects partners who may have no symptoms and don't yet know they need a test.
Because syphilis can be caught again after successful treatment, ongoing condom use and regular testing, particularly if you or a partner change sexual partners, remain the most reliable way to catch any future infection early.
Syphilis in pregnancy
Syphilis can pass from a pregnant woman to her baby, which is why a syphilis test is a routine part of antenatal screening in the UK, usually offered early in pregnancy alongside other standard blood tests. An untreated infection during pregnancy can seriously affect a baby's health, but timely antibiotic treatment during pregnancy is effective and greatly reduces this risk.
If you're pregnant, planning a pregnancy, or think you may have missed antenatal screening, speak to your midwife, GP or a sexual health clinic promptly, treatment in pregnancy is safe and time-sensitive.
When to get tested and how we can help
Consider testing if you've had a new or casual sexual partner, if a partner has told you they've been diagnosed with an STI, if you notice a sore, rash or swollen glands that doesn't have an obvious explanation, or simply as part of routine sexual health checks. Because early syphilis so often causes no symptoms, regular testing matters even when you feel completely well.
How often makes sense depends on your circumstances: people with a single long-term partner may only need testing occasionally, while those with new or multiple partners are generally advised to test more often, roughly every three to six months is a common starting point, adjusted to your own risk. If you're ever unsure, it's reasonable to simply ask rather than guess.
Our clinical team can arrange confidential STI testing and talk through timing, results and next steps, including referral for treatment where needed. Advice is always tailored to your personal history and circumstances, subject to suitability.
Frequently asked questions
How soon after exposure do syphilis symptoms appear?
Usually two to three weeks, though it can range from around ten days to three months. Many people notice nothing at all in the early stages, which is why testing rather than waiting for symptoms is the more reliable approach.
Can syphilis be treated successfully?
Yes. Early-stage syphilis usually responds well to a course of antibiotic injections, and later stages can still be treated effectively, though the course may take longer. Follow-up blood tests confirm the treatment has worked.
Is syphilis testing free and confidential in the UK?
Yes. NHS sexual health services offer free, confidential syphilis testing to everyone regardless of age, gender or background, and your GP won't be told about the visit without your permission.
Can you have syphilis with no symptoms?
Yes, this is common, particularly once the initial sore has healed. The infection can stay in the body without any visible signs for months or years while remaining detectable on a blood test.
Does syphilis affect pregnancy?
It can, which is why a syphilis test is offered as standard antenatal screening. If found, treatment during pregnancy is safe and greatly reduces the risk to the baby, so prompt testing and treatment matter.
What happens if I'm allergic to penicillin?
Tell the clinic when you book. An alternative antibiotic can usually be used, and your treatment and follow-up will be planned around it.