Syphilis: Symptoms, Causes, Testing & Treatment

What is syphilis?

Syphilis is a sexually transmitted infection (STI) that when left untreated can lead to serious long-term health complications.

Syphilis doesn’t always cause obvious symptoms. It’s important to get tested if you think you might have been exposed, even if you feel healthy, because it can cause lasting damage when left untreated.

How is syphilis transmitted?

Syphilis is most commonly spread through direct contact with syphilis sores, which usually appear on the genitals, anus, or mouth. The infection is transmitted during vaginal, anal, or oral sex. Sharing unwashed sex toys can also increase the risk of transmission.

While using male or female condoms and dental dams reduces the risk, syphilis can still spread through skin-to-skin contact if sores are not covered.

Low-angle shot of a smiling couple close together against a blue evening sky

Symptoms of syphilis

The symptoms of syphilis vary depending on the stage of the infection, and they may not always be noticeable.

Early symptoms

These typically develop within a few weeks of exposure and include:

Small, painless sores on the genitals, anus, mouth, or other parts of the body
Swollen lymph glands, especially in the neck, armpits, or groin

Secondary symptoms

If left untreated, syphilis can progress to cause:

A blotchy red rash, often seen on the palms of the hands or soles of the feet
Skin growths around the vulva or anus
White patches in the mouth
Flu-like symptoms, including fever, tiredness, headaches, and joint pain
These symptoms can disappear on their own, but the infection remains in the body.

Latent syphilis

Without treatment, syphilis enters a latent stage where there are no visible symptoms. Over time, it can cause severe health complications, including meningitis, dementia, and stroke.

Getting tested for syphilis

If you think you may have syphilis, it’s crucial to get tested as soon as possible. Early diagnosis can prevent long-term health problems and reduce the risk of passing the infection to others.

You can get a syphilis test for free at NHS sexual health clinics, GUM clinics, or some GP surgeries. If you’re wondering how to test for syphilis or looking for the best test for syphilis, your clinician can arrange a syphilis detection test — typically a syphilis blood test (also called a blood test for syphilis) — alongside a physical exam and swab if needed. Testing usually involves:

A physical examination
A blood test
A swab of any visible sores

You may also be offered tests for other STIs during your visit.

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How is syphilis treated?

Syphilis is treated with antibiotics, usually penicillin. Treatment typically involves one to three injections, although some cases may require a longer course of antibiotic tablets (10–28 days). Whether you’re exploring syphilis treatment for the first time or want to know how to treat syphilis after a previous course, your GP or sexual health clinic can talk you through the options — and while there’s no over-the-counter syphilis cure, prompt treatment for syphilis is highly effective in nearly all cases.

It’s important to complete the full course of treatment and follow any advice from your healthcare provider. Partners may also need to be tested and treated to prevent reinfection.

Syphilis is caused by the bacterium Treponema pallidum and develops in stages. In the primary syphilis stage, you may chancre-develop a chancre — a single painless sore — at the site of infection. Secondary syphilis can follow, where you might rash-develop a rash or a mucous patch in the mouth, along with swollen lymph nodes, as you lymphadenopathy-develop lymphadenopathy. If untreated, it can move into latent syphilis, with no visible symptoms, and eventually tertiary syphilis, where serious complications can develop.

Yes — if left untreated for years, syphilis can cause serious complications beyond the skin. For example neurosyphilis (where the infection affects the brain and nervous system) or cardiovascular syphilis (where the infection affects the heart and blood vessels). This is why it is important to diagnose syphilis as early as possible, before it causes lasting harm.

Yes. If someone has syphilis during pregnancy — itself typically sexually-transmitted between partners — the infection can congenitally-transmit to their baby, resulting in congenital syphilis. This is why routine antenatal screening for syphilis is so important — early detection allows treatment before the infection can infect the baby.

Syphilis is usually penicillin-treated with one or more injections, though some people are antibiotic-treated with a longer course of tablets if penicillin isn’t suitable. Treatment is highly effective at clearing the infection, especially when started before it reaches the syphilitic, neurosyphilitic, or cardiovascular stages — but it can’t undo any damage the infection has already caused, which is why early testing matters.

Syphilis: Symptoms, Causes, Testing and Treatment

What is syphilis?

How is syphilis transmitted?