Everything you need to know about Syphilis

By Chris Williams, updated 1 year ago in Health / Sexual health

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Everything you need to know about syphilis: symptoms, treatment, how to avoid it and how it interacts with HIV.

In this article:

What is Syphilis?

Syphilis is a chronic, curable sexually transmitted infection (STI) that is caused by bacteria called Treponema pallidum. If left untreated, it can result in serious health complications as well as increasing the possibility of onward transmission to other people.

An overview of Syphilis

The earliest known cases of syphilis date back to over 500 years ago and although humankind has been able to effectively treat it since around 1910, we don’t yet have biomedical options to help prevent it. The rates of syphilis infections have been increasing in Australia over the past five years, though certain populations are more affected than others. These include men who have sex with men, people living with HIV and Aboriginal and Torres Strait Islander people.

How is Syphilis transmitted?

Syphilis can be acquired from someone who currently has syphilis through skin-to-skin contact, typically during sex, or through sharing injecting equipment. Syphilis is highly infectious when a sore (known as a chancre) or rash is present, but it’s also possible to acquire it before someone knows they have it and when someone doesn’t have any sores.

Chancres may be present in, on or around a guy’s dick, arse, or mouth. They may not always be visibly noticeable or feel painful, which means you or your sexual partners might not always know they are there.

Syphilis is not transmitted through sharing cutlery, other household objects or by sharing towels, clothing or bathrooms.

“…syphilis treatment options are straightforward and highly effective, so getting tested can help ensure you stay healthy.”

Besides avoiding all forms of skin-to-skin contact, using condoms every time you have sex remains the most effective option to help prevent syphilis acquisition. Though it’s important to know that condoms don’t always fully cover affected areas and if you’re not using them for oral sex, or dams for rimming, there’s still the possibility of acquiring syphilis or another STI.

Going for regular sexual health tests is the only way to be sure if you do or don’t have syphilis. And even if you do, highly effective, straightforward treatment is available to cure syphilis.

How is Syphilis detected and tested for?

As is the case with many STIs, someone who has syphilis may or may not experience noticeable symptoms. This means you might not be able to tell if you or a sexual partner has syphilis. It’s important to go for tests at least every three to six months, even if you don’t notice anything unusual. If you do notice any symptoms, it’s best to avoid all sexual contact and see a healthcare professional or sexual health specialist as soon as possible.

Testing for syphilis is done by collecting a blood sample which is sent away for laboratory testing. Results are usually available within one week. Testing is very reliable, but does include a window period of anywhere between two to 12 weeks.

What is the STI window period?

window period is the time between coming in to contact with an STI and it showing up on a test. This means that a negative test result indicates you don’t have syphilis as of up to 12 weeks ago. If you’ve had sex since then, there’s the possibility you could have come in to contact with syphilis in the meantime, which won’t show up until your next test. What’s important to know is that syphilis treatment options are straightforward and highly effective, so getting tested can help ensure you stay healthy.

“…being treated for syphilis does not prevent the possibility of acquiring syphilis again.”

You can discover more about sexual health testing and where you can go in Eight reasons why you should get an STI test, even if you don’t think you need one.

What are the signs and symptoms of Syphilis?

Without treatment, syphilis typically progresses through various stages that can last for weeks, months or even years. Each stage may include these signs and symptoms, though they are not always guaranteed:

Primary stage 

There might be one or more sores (chancres) at the site of where syphilis entered the body. Because sores can be painless and hidden, their presence can easily go unnoticed. Sores may last between three and six weeks and will typically heal whether treated or not. Even if a sore goes away, this does not mean someone is cured of syphilis — treatment is still necessary to cure the infection and will prevent progression to the next stage.

Secondary stage

There might be skin rashes or sores in the mouth or arse. A rash may appear on palms of the hands or soles of the feet, or even elsewhere on the body, presenting as rough, red or reddish brown spots. The rash is not usually itchy and could be so faint that it’s entirely unnoticeable. Other symptoms may include fever, swollen lymph glands, sore throat, headaches, weight loss, patchy hair loss, muscle aches and general fatigue. Symptoms will typically go away whether treated or not. Even if symptoms go away, this does not mean someone is cured of syphilis — treatment is still necessary to cure the infection and will prevent progression to the next stage.

Latent stage

During the latent stage of syphilis there are no noticeable signs or symptoms. This is a period of time when someone still has syphilis in their body but has not yet progressed to tertiary syphilis. This stage may last for several years.

Tertiary syphilis

Although most people who have not received treatment for syphilis do not develop tertiary syphilis, it is a rare possibility. The infection can affect the heart and blood vessels, and the brain and central nervous system. If left untreated, tertiary syphilis can damage internal organs and may be fatal. Neurosyphilis is a chronic infection of the brain or spinal cord occurring in people who have had untreated syphilis for many years. The presence of HIV may accelerate the rate of progress of neurosyphilis.

How does Syphilis affect HIV?

For people living with HIV, syphilis may present more serious health concerns as it can progress more quickly and severely. However, early diagnosis and treatment can prevent progression of syphilis, avoiding long-term complications including damage to the heart and brain, or even premature death. Testing often and treating early are particularly important to stay healthy.

“For people living with HIV, syphilis may present more serious health concerns as it can progress more quickly and severely.”

For people living with HIV who maintain an undetectable viral load through treatment, the presence of syphilis or other STIs appears to have no, or very little impact on viral load. However, for people living with HIV not on treatment, the presence of syphilis may cause a significant increase in viral load, increasing the possibility of transmitting both syphilis and HIV.

For people who do not have HIV, the presence of syphilis can increase the likelihood of acquiring HIV if exposed to the virus.

How can Syphilis be prevented?

Using condoms every time you have sex helps provide protection against syphilis. This goes for oral sex including rimming, anal sex, and front hole sex with trans-men. While condoms do a great job of helping to reduce the possibility of acquiring or transmitting syphilis, they do not eliminate the risk completely. This is because condoms do not always cover affected areas of skin anywhere on or in the body where a sore or rash is present.

Does PrEP prevent Syphilis transmission?

While we now have highly effective biomedical options for preventing HIV such as using PrEP for people who are HIV negative, or preventing onward transmission by managing an undetectable viral load for at least six months for people living with HIV, neither of these HIV prevention strategies offer any protection against syphilis or other STIs.

“Besides avoiding all forms of skin-to-skin contact, using condoms every time remains the most effective option to help prevent syphilis.”

Is there a vaccine for Syphilis?

Although we don’t yet have biomedical solutions for preventing syphilis, breakthrough research from the University of Victoria in Canada was announced in February 2017 and shows promising results for a possible syphilis vaccine, though this may be several years away yet.

Post-exposure prophylaxis for Syphilis

Around the same time, news from the 2017 Conference on Retroviruses and Opportunistic Infections showed that using broad-spectrum antibiotic, doxycycline, as a post-exposure prophylaxis soon after sex did demonstrate a significant drop in syphilis infections.

Further research into the possibility of using antibiotics this way is required before we’re likely to see any major changes in syphilis prevention options. In the meantime, physical barrier devices such as dams and condoms are still the best option for preventing syphilis and other STIs.

How to treat Syphilis

Highly effective treatment is available for syphilis and the sooner someone is treated the better. Health problems experienced as a result of damage from tertiary syphilis may not be improved, even when syphilis is cured.

Treatment for primary or secondary syphilis usually involves a single dose of Benzathine penicillin administered by injection. Treatment for tertiary syphilis may involve three penicillin injections each administered one week apart. Alternative and effective treatments are still available for people who have intolerance to penicillin.

So far, there are no strains of syphilis that show resistance to penicillin as a first-line treatment.

After receiving treatment for syphilis, you may be requested to return to your healthcare provider or sexual health specialist for a test to ensure the treatment has been successful. It’s important to know that being treated for syphilis does not prevent the possibility of acquiring syphilis again.

Can you have sex after a Syphilis diagnosis?

As with treatment for most STIs, it’s necessary to avoid any kind of sexual contact for at least seven days after completing treatment for syphilis to prevent the possibility of onward transmission. It’s also advisable to avoid any sexual contact with partners from the last three months in the case of primary syphilis, or six months in the case of secondary syphilis, until they have been tested and treated if necessary.

“…it’s necessary to avoid any kind of sexual contact for at least seven days after completing treatment for syphilis.”

Should you tell sexual partners that you have Syphilis?

If you are diagnosed with syphilis, it’s advisable that all of your sexual partners from the last few months also go for sexual health tests. If you had sex while a sore or rash was present, they may also require treatment. You can notify sexual partners directly, or by using an anonymous notification service.


  • Syphilis can be acquired or transmitted through skin-to-skin sexual contact, or through sharing injecting equipment
  • Having syphilis doesn’t always guarantee having symptoms, so you might not be able to tell if you or somebody else has syphilis
  • The best way to enjoy sex while avoiding syphilis is to use condoms for all types of sex
  • Going for regular sexual health tests will help identify syphilis early
  • Syphilis can be cured with highly effective, straightforward treatment

You can discover more sexual health resources in our Knowledge Hub.