This page is general health information, not medical advice. It cannot tell you whether you have an infection. A clinician can, and the testing options on this site are a good place to start.

Syphilis is a bacterial infection that spreads through sexual contact and from a pregnant person to a baby. It is also one of the few STIs where the science is unusually clear: it can be found with blood tests, and it can be cured with treatment from a clinician.

This guide takes a science-focused look at the infection. It covers the organism behind it, what researchers have observed, how the stages unfold, how the blood tests work, and what to know about the safety of treatment. It also covers where Philadelphia residents can get tested for free or at low cost.

Anyone who is sexually active, of any gender or orientation, can get syphilis. Testing is a routine health step, not a judgment.

The short answer: is syphilis curable?

Yes. The CDC STI Treatment Guidelines (2021) say syphilis is curable with the right antibiotic from a clinician. Penicillin is the preferred treatment for every stage. A clinician decides the exact medicine and how it is given, based on the stage and the person's health.

Treatment stops the infection from getting worse. It does not undo damage that has already happened. That is one reason earlier testing matters.

Being cured once does not protect against getting syphilis again. The CDC notes that a person can be infected more than once, so regular testing can still make sense after treatment.

The organism: what researchers know about Treponema pallidum

Syphilis is caused by a spiral-shaped bacterium called Treponema pallidum (subspecies pallidum). It is a spirochete, a thin, corkscrew-shaped microbe that moves by twisting.

Research suggests several features of this bacterium explain why syphilis behaves the way it does:

It is hard to grow in a lab. For most of the history of syphilis research, the bacterium could not be reliably cultured. That is why diagnosis relies on blood tests that detect the body's response, rather than on growing the germ.
Its outer surface has few exposed proteins. Researchers have observed that this may help it avoid some immune responses, which fits with the infection lasting for years if untreated.
It spreads through tissue and blood. The CDC describes the infection as moving through the body in stages, with symptoms that can come and go.
It has stayed sensitive to penicillin. The CDC guidelines continue to list penicillin as the treatment of choice. This is the main reason syphilis remains curable.

These are laboratory and clinical observations. They help explain the patterns clinicians see, but they do not replace a test or an exam.

Syphilis symptoms by stage

The CDC describes syphilis in stages. Many people have mild symptoms or none at all, and symptoms can be mistaken for other conditions. Having no symptoms does not tell anyone whether they have the infection. Only a test can.

Primary stage: a sore

The first sign is often a single sore called a chancre. The CDC says it is usually firm, round and painless. It appears where the bacteria entered the body, such as the genitals, anus, rectum or mouth.

Because it can be painless and may be inside the body, it is easy to miss. The CDC says the sore typically appears about 3 weeks after exposure, with a possible range of 10 to 90 days. It heals on its own, usually in 3 to 6 weeks. Healing does not mean the infection is gone.

Secondary stage: syphilis rash and other signs

The syphilis rash is the best-known sign of the secondary stage. The CDC describes it as often rough, reddish-brown spots that can show up on the palms of the hands and soles of the feet. It can also appear on the chest, back or elsewhere, or look quite different. It usually does not itch.

Other secondary symptoms the CDC lists include:

Fever and tiredness
Sore throat
Swollen lymph nodes
Patchy hair loss
Headaches and muscle aches
Weight loss
Wart-like growths in warm, moist areas of the body

These signs also fit many other conditions, including common viral illnesses and skin problems. A clinician can tell the difference with an exam and a blood test. A rash on its own is not a diagnosis in either direction.

Latent stage: no signs

After the secondary stage, the infection can go quiet. The CDC calls this the latent stage. There are no visible symptoms, but the bacteria remain in the body. Blood tests can still detect the infection during this time.

Tertiary stage and other complications

The CDC says that without treatment, a small share of people go on to develop tertiary syphilis, years or even decades later. It can affect the heart, blood vessels, brain and nervous system. Syphilis can also reach the eyes, ears or nervous system at any stage. Symptoms such as vision changes, hearing changes, severe headache or confusion are reasons to seek care promptly.

Congenital syphilis

When a pregnant person has untreated syphilis, the infection can pass to the baby. The CDC says this can cause serious problems, including miscarriage, stillbirth and health problems in the newborn. Treatment during pregnancy can prevent this, which is why screening in pregnancy matters.

Why the national rise matters

The CDC's STI surveillance reports show that syphilis cases have risen in the United States over the past several years. The increase has included primary and secondary syphilis and congenital syphilis.

For readers, the practical meaning is simple. When an infection becomes more common, the chance that a person will encounter it goes up. The CDC also notes that many people do not have symptoms and may not know they have it. This is why screening, and not only symptom-checking, is part of the public health response.

The U.S. Preventive Services Task Force recommends syphilis screening for people at increased risk, and for all pregnant people. A clinician can help a person work out whether they fall into those groups, and how often testing makes sense.

Philadelphia and Pennsylvania data

The most recent state-level figures available here come from CDC STI Surveillance 2023. They show how common syphilis and other bacterial STIs were in Pennsylvania that year:

Infection (Pennsylvania, 2023)	Rate per 100,000 people	Cases
Primary and secondary syphilis	9.1	1,179
Gonorrhea	144.7	18,758
Chlamydia	421.2	54,600

Source: CDC STI Surveillance 2023, state tables. These are reported cases, so they reflect who was tested and diagnosed as well as who was infected.

A separate citywide syphilis figure for Philadelphia was not available in the sources used for this page. The Philadelphia Department of Public Health is the best place to ask for current local numbers.

Pennsylvania rules also shape how syphilis is tracked. Under 28 Pa. Code 27.21a, syphilis at all stages, along with HIV, chlamydia and gonorrhea, must be reported by health care practitioners and facilities within 5 work days after being identified. Reporting is how health departments follow trends and offer partner services. The City's STD Control Program says it offers partner services, meaning referral, testing and treatment for the sex partners of a person with an STI.

How syphilis testing works: the blood tests

Most syphilis diagnoses are made with blood tests. The CDC guidelines describe two kinds, and clinicians usually use both together. Neither type alone gives the full picture.

Non-treponemal tests

These tests (commonly called RPR or VDRL) look for antibodies that the body makes in response to damage from the infection. They have a useful feature: they give a number called a titer.

Research and clinical experience suggest that the titer tends to fall after successful treatment. That makes these tests useful for follow-up. They can sometimes read positive for reasons other than syphilis, so a second type of test is used to confirm.

Treponemal tests

These tests look for antibodies aimed specifically at the syphilis bacterium. The CDC says they usually stay positive for life, even after successful treatment. That means they are good at showing that a person has been exposed at some point. They are not used to measure whether treatment worked.

Two testing orders

The CDC guidelines describe two ways labs combine these tests. In the traditional order, the non-treponemal test comes first, and a treponemal test confirms. In the reverse order, the treponemal test comes first. Either way, results from both tests are read together by a clinician, who will explain what they mean in your situation.

Timing and repeat testing

Antibodies take time to appear. A test very soon after an exposure may not show an infection that is still early. The CDC says the sore, if present, usually appears in about 3 weeks, within a range of 10 to 90 days. A clinician can say whether a repeat test makes sense after a recent exposure, and when.

A clinician may also test fluid from a sore directly under a microscope in some settings. That is a clinician's decision, based on the situation.

Syphilis treatment: what a clinician prescribes

Syphilis treatment is prescribed by a clinician. The CDC STI Treatment Guidelines (2021) name penicillin as the preferred treatment at all stages. The form of penicillin, and how long treatment lasts, depend on the stage and on the person. This page does not list doses, because those are a clinician's decision.

Some key points from the guidelines:

Stage matters. Earlier infection generally needs a shorter course than infection that has been present longer or one that involves the eyes, ears or nervous system.
Pregnancy. The CDC says penicillin is the only recommended treatment for syphilis in pregnancy. A pregnant person who reports a penicillin allergy is usually referred for allergy evaluation so that penicillin can still be used.
Partners. A clinician may recommend that recent sex partners be tested and sometimes treated. Pennsylvania's Expedited Partner Therapy Act (Act 147 of 2022) lets a practitioner prescribe or furnish antibiotics for certain STIs to partners without examining them, following CDC guidance. CDC's legal-status page for Pennsylvania has the details. Which infections are covered in practice is something to confirm with a clinician or the health department.
Avoiding sex until cleared. The CDC advises people to avoid sexual contact until treatment is complete and any sores have healed, or as the clinician advises.

Safety profile and contraindications of treatment

Penicillin has a long record of use. Research and decades of clinical experience suggest it is generally well tolerated, but a clinician should know about a person's history first.

Penicillin allergy. This is the main safety question. Many people who think they are allergic turn out not to be when tested. A clinician can ask about past reactions, arrange allergy testing, or choose another medicine when appropriate. The CDC says alternatives are less well studied for syphilis, which is why clinicians weigh this carefully, and why close follow-up matters.
Jarisch-Herxheimer reaction. The CDC describes this as a short-lived reaction that can happen within the first day after treatment starts. It may include fever, chills, headache and muscle aches. It is not an allergy. A clinician can explain what to expect and when to call.
Pregnancy. Treatment is important for the health of the pregnancy, and the clinician may watch more closely for reactions.
Other medicines and conditions. Tell the clinician about everything you take and any health conditions, including a weakened immune system or HIV.

Call a clinic or seek urgent care for symptoms such as trouble breathing, swelling of the face or throat, or hives after any medicine.

Follow-up blood tests after treatment

Treatment is not the last step. The CDC guidelines call for follow-up blood tests so that a clinician can see whether the non-treponemal titer is falling as expected. These tests happen at set intervals, which the clinician chooses based on the stage and on whether the person has HIV.

Some people have a titer that stays low but positive for a long time. A clinician can explain what that means. A titer that does not fall as expected, or symptoms that return, may lead to more evaluation or more treatment.

Keeping follow-up appointments is the most reliable way to know treatment worked.

Prevention: condoms, PrEP-related care and doxy-PEP

The CDC says condoms, used consistently and correctly, lower the chance of syphilis when they cover the sore or the area where it could spread. They do not cover every possible area of contact, so they reduce risk but do not remove it.

In 2024 the CDC issued guidance on doxycycline post-exposure prophylaxis (doxy-PEP). It describes the use of doxycycline after sex to lower the chance of syphilis, chlamydia and gonorrhea for certain groups, such as gay, bisexual and other men who have sex with men, and transgender women, who have had a bacterial STI in the past year. It is a prescription decision made with a clinician. This page did not find a published Philadelphia program for it, so ask a clinic or the health department what is available.

Many people who get tested for STIs also use the visit to talk about HIV prevention. The City says Health Center 1 offers PrEP counseling to people who test negative for HIV. The Pennsylvania Department of Health reports that federal rules require most insurers to cover HIV PrEP medication with no out-of-pocket cost for insured people. For telehealth PrEP, Philadelphia's Philly, Keep On Loving program offers TelePrEP online and by phone. Its page does not state cost or eligibility, so check the program directly at 215-985-2437.

Quality indicators: how to choose reliable testing and care

The idea of sourcing and quality matters here in a different sense: where a test is done, and who reads it. Signs of reliable care include:

A public health or established clinic. The Philadelphia Department of Public Health and community health organizations follow CDC guidance.
Both test types, interpreted by a clinician. A result should come with an explanation, not just a number.
A plan for follow-up. Good care includes repeat blood tests and, when needed, partner services.
Clear information about cost. Clinics should be able to tell you what you will pay before a visit.
Privacy. Pennsylvania law lets minors consent to testing and treatment for venereal disease, according to the Guttmacher Institute's state summary, which lists no minimum age and no parental-notification provision. Check with the clinic about its own policies.

Free and low-cost syphilis testing in Philadelphia

These are options listed by the City of Philadelphia and by CDC's GetTested directory. Services and hours can change, so call before you go.

STI clinic at Health Center 1 (Philadelphia Department of Public Health)

Address: 1930 S. Broad St., Fl. 2, Philadelphia, PA 19145
Phone: (215) 685-6570 or (215) 685-6575
Cost: free
How it works: walk-in only, first-come first-served. The City says anyone over 13 can get testing and treatment.
Hours (per the City): Monday and Wednesday 7:45 a.m. to 7 p.m.; Tuesday, Thursday and Friday 7:45 a.m. to 4 p.m. On the first Wednesday of each month the clinic opens at 1 p.m. On very busy days it may close earlier.

The City's page also describes this clinic as offering HIV testing, PrEP and PEP, and several vaccines.

Planned Parenthood Southeastern Pennsylvania

CDC's GetTested listings show two Philadelphia health centers that test for syphilis, HIV, chlamydia, gonorrhea and herpes. Both list sliding-scale fees and say an appointment is required.

Elizabeth Blackwell Health Center, 1144 Locust St, Philadelphia, PA 19107, (215) 351-5560
Castor Avenue Health Center, 8210 Castor Ave, Philadelphia, PA 19152, (215) 745-5966

Jonathan Lax Treatment Center (Philadelphia FIGHT Community Health Centers)

1233 Locust St, 4th Fl, Philadelphia, PA 19107, (215) 790-1788. The CDC GetTested listing says an appointment is required and lists free HIV and STI tests. It also says insurance, Medicaid and Medicare are accepted. Hours are not published there, so call the clinic.

Mazzoni Center

1201 Locust St., Philadelphia, PA 19107, (215) 985-9206. The City lists Mazzoni Center as a community testing site for HIV, STI and hepatitis C testing, PrEP and PEP, with hours of Monday and Saturday 10 a.m. to 6 p.m. and Tuesday through Friday 10 a.m. to 8 p.m. The City's page does not state a cost, so ask when you call.

Other community sites

The City also lists Bebashi - Transition to Hope (4101 Woodland Ave. and 1237 Spring Garden St., (215) 769-3561) and Courage Medicine (3751 Island Ave, Suite 201, 267-217-3217) as community testing sites. Neither page states a cost, so ask each directly. For the full local list, see the clinics we list for Philadelphia.

For a wider look at what is available, including how to prepare for a visit, read our guide to where to get tested for STDs in Philadelphia.

Testing from home

The City's Philly, Keep On Loving program says Philadelphia residents can order free HIV or STI test kits, condoms and lube online. Its page does not list eligibility or which infections each kit covers, so check the order page at phillykeeponloving.com before ordering.

Other places

The CDC's GetTested tool at gettested.cdc.gov lets you look up testing sites by ZIP code. The City's health center questions line is 311, and the STD Control Program can be reached at (215) 685-6740.

If you are pregnant

Pennsylvania's rule at 28 Pa. Code 27.89 says a physician attending a pregnant woman must tell her that a blood sample will be taken for a syphilis test at the first exam or within 15 days, unless she objects. A second test in the third trimester, and testing at delivery, are required only in counties the Department designates in the Pennsylvania Bulletin. Whether Philadelphia is on that list was not confirmed here, and the City has also posted a Board of Health amendment on this topic. Ask your prenatal provider or the health department what applies to you.

Questions to bring to a visit

Which syphilis tests are you running, and when will I get results?
Is there a reason to repeat the test later?
If treatment is needed, what are my options, given any allergies?
When are my follow-up blood tests?
How do I let partners know, and can the health department help?
Should I also be tested for HIV, hepatitis C or other infections?

The takeaway

Syphilis has stages, and the signs, including the syphilis rash, can be subtle or easy to confuse with other conditions. Blood tests, read together by a clinician, are how it is found. It is curable with penicillin from a clinician, and follow-up blood tests show whether treatment worked.

If you have questions about a possible exposure, a rash, or a sore, a free or low-cost visit in Philadelphia is a practical next step.

Syphilis in Philadelphia: Symptoms, Testing and Treatment