Medically Reviewed By William C. Lloyd III, MD, FACS

What is syphilis?

Syphilis is a sexually transmitted disease (STD) caused by the bacterium Treponema pallidum. People get syphilis from sexual contact with an infected person by means of direct contact with a syphilis sore (chancre). An infected person who is pregnant can also pass syphilis to the fetus. This congenital form of syphilis can be fatal for the fetus. A simple blood test can check for this bacterial infection.

Syphilis usually starts with a single, painless sore on the genitals, anus or mouth. Many people do not notice this first sign of the infection. Without treatment, the disease will progress through stages. Later syphilis symptoms include a rash, fever, muscle aches, and hair loss. Eventually, syphilis can damage the bones, brain, nerves, eyes, heart, and blood vessels.

Syphilis can be prevented and treatment in the early stages is effective. Despite this, transmission both through sexual contact and during pregnancy has been on the rise in the United States, according to the CDC (Centers for Disease Control and Prevention).

Any person of any age who engages in sexual activity can contract and pass on syphilis. This includes people who are heterosexual, homosexual, and bisexual. The more sexual partners a person has, the greater the risk of contracting syphilis.

Left untreated, a syphilis infection can stay in the body for years. It can progress to serious or life-threatening complications, such as dementia, aortic aneurysm, and stillbirth in a pregnant person. Practicing safe sex, getting regular medical care, and seeking early, regular prenatal care can help reduce the risk of serious complications of syphilis.

What are the different stages of syphilis?

Without treatment, syphilis progresses in four stages. While the stages may overlap, the infection generally follows these stages:

  • Primary syphilis: This is the first stage that develops between 10 days and 12 weeks after exposure. Typically, a painless sore on the genitals, anus or mouth develops during this stage. It heals on its own in about 3 to 6 weeks. This stage is very contagious.

  • Secondary syphilis: This second stage usually begins within 2 to 8 weeks of the sore healing. However, it can take up to six months to progress to this stage. Symptoms can affect any body part or system, but a syphilis rash is typical. The symptoms in this stage can recur on and off for months or years. This stage is very contagious.

  • Latent syphilis: In this hidden stage, there are no symptoms or signs of the infection. It can last for years. For many people, the symptoms never return and the disease does not progress because the infection cures itself. The infection may still be contagious early in this stage—within the first 12 months of the infection. It generally is not contagious after that time, although someone who is pregnant can still pass it to their baby.

  • Tertiary syphilis: Up to one-third of people with syphilis will progress to this late stage. Symptoms return as serious health problems due to organ damage and other conditions. It can take years and even decades for these problems to become evident. This stage is not contagious and can be fatal.

What are the symptoms of syphilis?

Syphilis is an infection that can stay in the body for years without early diagnosis and treatment. There are three symptomatic stages of syphilis, and each stage has distinct symptoms.

Symptoms of primary syphilis

Primary syphilis is the first stage of syphilis. Characteristics of primary syphilis include:

  • A painless lesion called a chancre develops any time from 10 days to three months after exposure.

  • The chancre generally appears on the genital area. It can also form on the lips, tongue or rectum if these areas have been in contact with a syphilis chancre on another person during oral or anal sexual contact. A chancre in the vagina, mouth or rectum is generally not easy to see. A person may not realize they have a chancre.

  • The chancre heals in 3 to 6 weeks.

Symptoms of secondary syphilis

Left untreated, syphilis progresses to a second stage. In this stage, the syphilis bacteria spread throughout the body and cause additional symptoms. Symptoms begin to appear about six weeks after the chancre has resolved and include:

Symptoms of tertiary syphilis

Symptoms of tertiary syphilis may not appear for 10 to 20 years after initial syphilis infection. During this time, syphilis can damage organs, such as the brain, heart, eyes, blood vessels, liver, bones, and nerves, leading to serious complications.

Symptoms of tertiary syphilis include:

What causes syphilis?

The bacterium Treponema pallidum causes syphilis. Syphilis spreads from one person to another during sexual contact that involves vaginal, oral, or anal sex involving direct contact with a syphilis sore (chancre). The infection also can pass to the fetus during pregnancy. This is congenital syphilis, which can be fatal.

Anyone who engages in sexual activity can contract and pass on a syphilis infection.

What are the risk factors for syphilis?

A number of factors increase the risk of catching syphilis. Risk factors include:

  • Being a male who has sex with male partners

  • Being born to a person with syphilis

  • Having HIV/AIDS

  • Having multiple sexual partners (the more sexual partners a person has, the greater the risk of contracting syphilis)

  • Having unprotected sex, including vaginal, oral and anal sex, with a partner who has had one or more other sexual partners

  • Using recreational drugs or alcohol, as this can lower inhibitions and lead to unsafe sexual practices

How do you prevent syphilis?

A person can transmit syphilis to others even when there are no symptoms. People can lower their risk of contracting and spreading syphilis and developing complications by:

  • Abstaining from sexual activity or engaging in sexual activities only within a mutually monogamous relationship in which neither partner is infected with syphilis or has risk factors for the infection

  • Avoiding alcohol and recreational drug use

  • Getting regular, routine medical care

  • Practicing safe sex and using a new latex condom for each sex act

  • Seeking medical care as soon as possible after possible exposure to syphilis or after high-risk sexual activity

  • Seeking prenatal care early and regularly during a pregnancy

How do doctors diagnose syphilis?

To diagnose syphilis, the healthcare professional will take a medical history, perform an exam, and order testing. The practitioner may order tests for other STDs too. Questions a doctor may ask include:

  • What symptoms are you experiencing?

  • When did these symptoms begin?

  • Are you sexually active?

  • When was your last sexual interaction?

  • How many sexual partners do you have? Are they the same sex?

  • How long have you been with your partner or partners?

  • How many partners have you had in the past year?

  • Do you or your partner(s) use recreational drugs?

  • What kind of birth control do you use?

  • What kind of protection do you use?

  • Have you ever had an STD?

  • What other medical conditions do you have?

  • Are you pregnant or is there a possibility you could be pregnant?

Depending on the stage of infection, the doctor may examine the sore itself or the rash or other symptoms. This may include a neurological and vision exam. Testing is necessary to confirm the diagnosis. Depending on the stage of the infection, testing may include:

  • Lab testing of a fluid or skin sample from the chancre to look for bacteria

  • Blood testing to check for antibodies to the syphilis bacteria, which can still be present years after the initial infection. Doctors can use this to diagnose a past infection.

  • Lumbar puncture (spinal tap) to diagnose neurologic complications of syphilis

Sexual partners of people who test positive for syphilis should also be tested.

How do you treat syphilis?

With early diagnosis, syphilis treatment is straightforward and will cure the infection. It consists of an injection of an antibiotic into a muscle. Penicillin is the preferred antibiotic. More doses of penicillin may be necessary for people who have had syphilis for more than a year. This may require three doses with one week between each dose.

For serious cases that affect the eyes, inner ears, or brain, the doctor may administer penicillin as an IV (intravenous) infusion. This treatment may last up to 14 days.

It is possible to have a reaction to syphilis treatment within 6 to 12 hours of the first dose. The name for it is Jarisch-Herxheimer reaction. It consists of fever, chills, headache, body aches, and sweating. Syphilis sores may also worsen. It usually subsides within 24 hours.

Doctors may use an alternate antibiotic for people who are allergic to penicillin. Penicillin desensitization may also be an option to allow allergic people to take the antibiotic.

The treatment plan will also include:

  • Abstaining from sexual activity until treatment is complete and tests show the infection is gone

  • Following-up with regular exams and blood tests until the doctor is certain the infection is gone 

  • Telling sex partner(s) so they can be tested and begin treatment if necessary 

Treatment will not prevent a person from getting syphilis again.

How does syphilis affect quality of life?

Before the era of penicillin, syphilis was a feared disease. It had a tremendous impact on quality of life. Today, it is rare for someone to have tertiary syphilis, which has the greatest physical effect on quality of life. With early detection and treatment, syphilis does not affect physical quality of life to any great extent. However, it can have an effect on mental, psychological and social quality of life.

Studies show partner notification for any STD can lead to social stigma, intense embarrassment, and fear of retaliation, domestic violence, or relationship loss. Research suggests there is greater shame and stigma with syphilis than with most other STDs, including HIV.

What are the potential complications of syphilis?

Complications of untreated syphilis can be serious and life-threatening. People can reduce the risk of serious complications by following the treatment plan.

Complications of syphilis include:

  • An increased risk for contracting HIV, which causes AIDS

  • Aortic aneurysm

  • Birth defects and stillbirth in up to half of affected pregnancies

  • Blindness

  • Dementia

  • Paralysis
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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2021 Dec 14
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