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. It has a reputation for being mysterious, mostly because it can look like many other things and can go quiet for years. It is also one of the more straightforward STIs to treat once it is found.

This guide takes a science-first look at the infection. It covers the organism behind it, the stages, what a syphilis rash can look like, how blood tests work, how treatment works, and what the safety picture looks like. It also covers what San Diego County's recent numbers show and where to get tested here.

Nothing here can tell you whether you have syphilis. Only a test and a clinician can do that.

What causes syphilis: the organism, in plain terms

Syphilis is caused by a bacterium called Treponema pallidum. It is a thin, spiral-shaped microbe. It does not survive well outside the human body, which is one reason it spreads through direct contact rather than surfaces.

The CDC explains that syphilis passes from person to person through direct contact with a syphilis sore. Sores can be on or around the genitals, anus or rectum, or in or around the mouth. This means syphilis can pass during vaginal, anal or oral sex. A pregnant person can also pass it to a baby.

A few features of the organism explain why syphilis behaves the way it does:

It moves through the bloodstream. Research suggests the bacterium can spread through the body early in infection. That is why symptoms can show up far from the original sore, including on the skin.
It is slow-growing. The CDC describes symptoms that can appear weeks after exposure and long quiet periods between stages.
It has not developed resistance to penicillin. The CDC STI Treatment Guidelines (2021) still list penicillin as the preferred treatment for all stages. This is a large part of why syphilis is curable.

There are no chemical "ingredients" to evaluate here, the way there would be with a supplement. The useful science is the biology of the bacterium, the way the body responds to it, and the quality of the tests and care used to find and treat it.

The stages of syphilis

The CDC describes syphilis in stages. Not everyone moves through every stage in an obvious way. Some people never notice a symptom at all.

Primary stage

The first sign is usually a sore, called a chancre. According to the CDC, it is typically firm, round and painless. Because it does not hurt, it can go unnoticed, especially if it is inside the mouth, vagina or rectum. It usually heals on its own, which can give a false sense that the issue has resolved. The bacterium is still in the body.

Secondary stage

Secondary syphilis often brings a skin rash and sometimes other symptoms. The CDC lists these among them:

Rash on one or more areas of the body
Fever and swollen lymph glands
Sore throat
Patchy hair loss
Headaches and muscle aches
Weight loss and tiredness

These symptoms can be mild and can come and go. Like the first sore, they usually resolve without treatment, even though the infection remains.

Latent stage

In the latent stage there are no visible signs or symptoms. The CDC notes the infection can stay in the body for years in this stage. A blood test is the main way it is found.

Late (tertiary) stage

The CDC says that without treatment, a small share of people go on to develop late-stage syphilis, which can affect the heart, blood vessels, brain and other organs. This is uncommon, and it is a main reason clinicians encourage testing and treatment earlier.

Nervous system, eye and ear involvement

The CDC also notes that syphilis can reach the nervous system, the eyes or the ears at any stage. Changes in vision or hearing, or severe headaches, are reasons to talk with a clinician promptly. Clinicians can order extra evaluation when this is a concern.

Syphilis symptoms and the syphilis rash

People often search for the syphilis rash because it is the most visible sign. Here is what the CDC and clinical references say about it, kept simple and non-graphic.

Timing. The rash is a feature of the secondary stage. It can appear while the first sore is healing or after it has healed.
Appearance. It is often described as rough, reddish-brown or pink spots. It can be so faint that it is overlooked.
Location. It can appear on the trunk, and the CDC specifically notes it may show up on the palms of the hands and the soles of the feet. It can also show up elsewhere.
Itch. The CDC says the rash usually does not itch.

Here is the important part. Many things cause rashes, including allergies, eczema, medications and other infections. A rash that looks a certain way does not confirm or rule out syphilis. A clinician can look at it and order a blood test to find out.

Likewise, a lack of symptoms does not tell anyone their status. The CDC is clear that syphilis can be present without any signs. That is why testing is based on exposure and risk, not on how someone feels.

Why the national rise matters

The CDC reports that syphilis has risen across the United States in recent years. The increase has been seen among men and women, across many racial and ethnic groups, and in congenital syphilis, which is syphilis passed to a baby during pregnancy.

Three reasons this matters, according to public health reporting:

It can be silent. Because symptoms can be missed or can fade, people may carry the infection without knowing and may pass it on.
It affects pregnancy. The CDC says congenital syphilis can lead to stillbirth, newborn death and lasting health problems for a baby. It is preventable with timely testing and treatment during pregnancy.
It interacts with HIV. The CDC notes that having a syphilis sore can make it easier to get HIV. Testing for one often goes together with testing for the other.

None of this is a reason for fear. It is a reason that routine, low-barrier testing is valuable, and that treatment works well when it is started.

How syphilis is tested: the two types of blood tests

Syphilis is most often found with a blood test. Sometimes a clinician also takes a swab from a sore. The CDC STI Treatment Guidelines (2021) describe two families of blood tests that are used together.

Treponemal tests

These look for antibodies the body makes in response to Treponema pallidum itself. Research suggests these antibodies usually stay detectable for life, even after successful treatment. That means a treponemal test can stay reactive long after the infection is gone.

Non-treponemal tests

These measure a different kind of antibody response, one tied to the damage the infection causes. The results are given as a ratio (a titer). The useful feature is that the number tends to go down after effective treatment. That makes these tests valuable for tracking whether treatment worked.

Why two tests

Each type can occasionally give a result that needs a second look. Using both helps a clinician interpret what is going on. The CDC describes two testing sequences. Some labs start with the non-treponemal test and confirm with a treponemal one. Others start with the treponemal test and follow up with the other. The order depends on the lab.

For you, this means one blood draw can lead to a request for more testing. That is a normal part of how the tests work. It does not mean something is wrong.

What about timing after exposure?

Antibodies take time to build, so a test very soon after an exposure may not show an infection. The CDC does not publish a single window period that applies to every situation, and this article will not guess at one. If you had a recent exposure, a clinician can tell you whether to test now, test again later, or both.

Who should be tested

The USPSTF recommends screening for syphilis in people at increased risk. It also recommends screening for all pregnant people. The CDC adds that anyone with symptoms, a partner who has been diagnosed, or a new sexual partner can reasonably ask a clinician about testing. Testing is useful for people of every gender and orientation.

Is syphilis curable?

Yes. Syphilis is curable with treatment from a clinician. The CDC says the infection can be cured with the right antibiotic. This is different from HIV, herpes and HPV, which are treatable or manageable but not curable.

Here is how treatment works at a high level:

Penicillin is the preferred medicine. The CDC STI Treatment Guidelines (2021) list penicillin as the recommended treatment for every stage, including in pregnancy.
A clinician decides the form and length. The type of penicillin and the number of visits depend on the stage and on the person's health. Those decisions belong to a clinician, so this article does not give doses or schedules.
Earlier is simpler. The CDC notes that treatment stops the infection from getting worse. It also notes that treatment cannot undo damage that late-stage syphilis has already caused, which is another reason not to wait.
Partners are part of care. A clinician may recommend that recent partners be tested or treated, so the infection does not pass back and forth.

Syphilis treatment is not something to attempt with leftover or borrowed antibiotics. The wrong medicine or the wrong length can leave the infection active while symptoms improve, and it makes later blood tests harder to read.

Follow-up blood tests after treatment

Treatment is not the end of the process. The CDC recommends follow-up blood tests so a clinician can confirm that the infection is responding.

Here is what that generally looks like:

The clinician repeats a non-treponemal test at set points after treatment. The timing depends on the stage and on factors like pregnancy or HIV status, so the clinician sets it.
The goal is for the titer to fall over time. The CDC describes a meaningful drop as the expected sign that treatment worked.
The treponemal test usually stays reactive for life. That is expected and does not mean the infection is still active.
If a titer does not fall as expected, or symptoms return, the clinician can investigate and discuss next steps.

Many people find the follow-up the least intuitive part. A blood test that stays positive for years can feel alarming. It is usually just the lasting antibody record.

It also helps to know that a past infection does not protect you from getting syphilis again. The CDC says people can be reinfected, so routine testing remains useful after treatment.

Safety profile and contraindications of syphilis treatment

Penicillin has been used for decades, and clinicians know its safety profile well. A few points are worth knowing before an appointment.

Penicillin allergy

The main contraindication is a true penicillin allergy. Tell the clinician about any past reaction. Many reported penicillin allergies turn out not to be true allergies, and a clinician can help sort that out. The CDC notes that for pregnant people, penicillin is the recommended treatment, so a clinician may evaluate the allergy carefully or arrange desensitization rather than switch to another medicine. For people who are not pregnant, clinicians may choose an alternative antibiotic.

A short-term reaction after the first treatment

The CDC describes the Jarisch-Herxheimer reaction. It is a short-lived response that can include fever, chills, headache and muscle aches, usually within the first day after treatment. Research suggests it is linked to the body reacting as the bacteria are cleared. It is not an allergy, and it generally passes. A clinician can tell you what to expect and which symptoms warrant a call.

Pregnancy

Pregnancy does not change the preferred medicine, but it raises the stakes for timely care. The USPSTF recommends syphilis screening for all pregnant people. For specific California requirements about when screening happens during prenatal care, ask your prenatal provider or the health department. The state rule was not something this article could confirm.

Doxycycline after sex (doxy-PEP)

The CDC's 2024 guidance discusses doxycycline taken after sex as a way to lower the chance of certain bacterial STIs, including syphilis, for some groups at higher risk. It is a prevention option, not a treatment for syphilis, and a clinician decides who it is right for. The Night Clinic at Hillcrest Family Health Center lists DoxyPEP among its services.

Sourcing and quality indicators: how to judge a test and a clinic

Since there are no products to source, the question becomes how to find reliable testing and care. Some practical quality indicators:

A clinician is involved. Good syphilis care includes someone who can interpret both blood tests, examine a sore or rash, and prescribe treatment.
The clinic explains what is being tested. Syphilis is not always part of a basic panel. Ask whether syphilis, chlamydia, gonorrhea and HIV are each included.
Results come with a plan. A reliable service tells you how results reach you, what happens if a result is reactive, and how follow-up is handled.
Confidentiality is explained. You should be told who sees your results and how reporting works.
Costs are clear up front. Public and community clinics can explain sliding scale pricing or fee waivers before you commit.

A reactive result is not a final answer by itself, since the two kinds of tests are read together. Clinicians use both to decide what a result means.

Syphilis in San Diego: the local numbers

Reporting by Times of San Diego on March 2, 2026, citing County of San Diego Health and Human Services Agency data for 2024, gives a snapshot for San Diego County:

Primary and secondary syphilis: 309 cases in 2024, down 35.8% from 481 in 2023.
Congenital syphilis: 31 cases in 2024, down from 36 in 2023. The same report says three stillbirths or neonatal deaths were recorded in 2024, the most since 2019.
Context: The same article reported 16,414 chlamydia cases and 6,021 gonorrhea cases in the county in 2024, both lower than in 2023.

These figures are county-wide, and the article did not list per-100,000 rates, so none are given here. State-level figures were not available to this article, so check the California Department of Public Health for statewide numbers.

The takeaway is balanced. Primary and secondary cases fell sharply in 2024. Congenital syphilis, though, remains a concern, and it is the reason prenatal screening gets so much attention.

Where to get tested for syphilis in San Diego

Several places offer free or low-cost testing. Details below come from each clinic's own page or from CDC directory listings. Hours and walk-in policies can change, so call first.

Family Health Centers of San Diego, Hillcrest

Hillcrest Family Health Center, at 4094 4th Avenue, lists STI screening and treatment, with walk-ins welcome Monday to Friday, 8:00 a.m. to 5:00 p.m. Call (619) 515-2300 for appointments or (619) 515-2545 for information. The clinic says it may be able to waive fees or help with insurance enrollment.

The Night Clinic at the same address lists free and confidential HIV testing and low-cost STI tests, Monday to Thursday, 5:00 to 9:00 p.m., with walk-ins welcome. Its page also lists PrEP, PEP and DoxyPEP.

San Diego LGBT Community Center

The Center, at 3909 Centre Street, is listed by the CDC's National Prevention Information Network as offering on-site syphilis, chlamydia and gonorrhea testing, rapid HIV testing and rapid hepatitis C testing, with no fee for services. The listing gives hours of Monday to Friday, 10:00 a.m. to 8:00 p.m. and Saturday, 10:00 a.m. to 4:00 p.m., and says to call for STD and HIV testing hours. Phone: 619-692-2077. Because sources differ on whether appointments are needed, confirm by phone.

County of San Diego Central Public Health Center

The county's sexual health clinic is at 5101 Market St, San Diego, CA 92114. The CDC GetTested listing says it offers free STI and HIV testing, charges based on income, and accepts insurance, Medicaid and Medicare. Call (619) 229-5400 to confirm eligibility. The listing says appointments are required, but other material suggests walk-ins, so ask when you call. Hours were not available.

Planned Parenthood, College Avenue

The College Avenue center at 4575 College Ave is listed on CDC GetTested as offering syphilis testing, with no appointment required and payment by insurance, Medicaid or sliding scale. Call (888) 743-7526. Hours were not listed.

For a fuller rundown of options and costs, see this guide to STD testing in San Diego, where to get tested and what it costs. You can also browse the local testing list.

The CDC's GetTested tool can also help you find nearby testing sites. UC San Diego Health's Owen Clinic runs a PrEP clinic (619-543-3995), but its page does not list STI testing, so it is not a syphilis testing site.

Privacy, minors and partners

Under California Family Code section 6926, a minor age 12 or older may consent to diagnosis and treatment of certain infectious and sexually transmitted diseases and to care related to STD prevention. Parents are not liable for payment. The Guttmacher Institute lists no parental notification provision for California, and the statute text does not mention one. If you are a minor, ask the clinic how billing and communication work.

On talking with partners: it is common to feel awkward. A clinician can explain what partners should know and which tests are worth asking about. The tone that works best is the plain one: "I was treated for an infection, and it is a good idea for you to be tested."

What to do next

Think about your recent exposures, symptoms and any pregnancy, and write them down for the visit.
Pick a clinic from the list above and call to confirm hours, walk-in policy and cost.
Ask which tests are included, and whether syphilis, HIV, chlamydia and gonorrhea are each covered.
If you are treated, keep your follow-up blood test appointments.
Ask your clinician when to test again, since reinfection is possible.

Syphilis is common enough to deserve routine attention and treatable enough that a positive result is not the end of anything. Getting tested is an ordinary, practical step.

Syphilis in San Diego: Symptoms, Testing and Treatment