How is syphilis transmitted?

Updated on:
February 16, 2022

The different ways syphilis can be transmitted

Anal, oral, and vaginal sex

Syphilis is commonly spread through direct contact with a syphilis-induced sore (chancre) during sex. With the developing sores and rashes usually found around the penis, vagina, anus, mouth, and fingers, this makes unprotected sexual contact extremely risky.

The transmission of syphilis relies on skin-to-skin contact with someone who is already infected, meaning that syphilis can still spread even if the infected individual doesn’t cum.

Oral sex is less likely than anal or vaginal sex  to spread syphilis, but there is still a chance. If a sore is present in the mouth, syphilis can spread through oral sex and even through kissing (least common).

Sharing sex toys

Just as exploring another’s body with your own opens you up to the risk of coming into contact with syphilis bacteria, the same reasoning applies to sex toys.

If a sex toy comes into contact with a sore, there is a chance that the bacteria will stick to the surface and transmit to the next person if it’s shared.

Sharing drug-injection equipment

Apart from contact-based transmission, syphilis is also transmittable by blood.

When an injection takes place, a small amount of blood goes into the needle and syringe. If you reuse the same injecting equipment, syphilis-infected blood poses the risk of contaminating anything it comes into contact with. Sharing this equipment with someone else could result in syphilis being transmitted.


Since syphilis is transmittable by blood, pregnancy can also result in the spread of syphilis to the infected person’s baby.

Studies have shown that a majority of babies born to someone that has untreated syphilis will have significant physical or mental complications or may die within the womb (stillborn) or shortly after as a newborn.

How is syphilis NOT transmitted?

Like most STIs, there are many myths present in terms of how syphilis is transmitted.

Syphilis does not spread through casual contact. This means that you can not get it from hugging, holding hands, coughing, sneezing, sharing food/drinks, sharing towels, or sitting on a toilet seat.

How to prevent the transmission of syphilis?


While the correct usage of condoms can reduce the risk for genital fluid-based STIs (gonorrhea, HIV, chlamydia), skin-contact transmission is a little more difficult.

Since syphilis is most commonly spread by someone coming into contact with a syphilis-induced sore, proper condom protection requires that the sore be covered as well. With sores being able to appear on other parts of the body apart from the genitals, a condom doesn’t always ensure protection. Any uncovered sore used in a sexual context has more risk.

Condoms do reduce the likelihood of spreading syphilis, but only if the sore is covered.

Dental dams

Similar to the limitations of condoms, any sores must be covered by the dental dam in order for its protection to be beneficial.

Wash and & wrap your sex toys

If you are going to share sex toys, make sure they are washed between each use and covered with a new condom. This helps reduce the likelihood that the bacteria left over from a chancre will come in contact between the users.

Don’t reuse drug-preparation equipment

If you do choose to inject drugs, do not reuse or share needles or any drug preparation equipment with someone else.

This includes sharing water to clean injection equipment, the containers used to dissolve the drugs, and filters. Make sure to use new materials (containers, filters, & needles) and clean water each time you prepare any drugs for injection. It’s also recommended to wipe down the injection site with an alcohol swab each time as well.

Regular testing

By making it a common practice to be tested for syphilis (and other common STIs), you limit the amount of time you can unknowingly infect others. Since many people infected with syphilis don’t present any symptoms (about 50%), testing is the best way to know for sure.

Syphilis treatments

If you have tested positive, making sure that you and all of your recent sexual partners are treated effectively is of the utmost importance to prevent further transmission of syphilis. To ensure the medication has time to work, all persons treated for syphilis are asked to avoid activities that could spread syphilis (i.e. sex) for 7 days after last dose of medication to allow time to get rid of every last bacteria.

For more information about treatments, see our article covering everything you need to know about syphilis treatments.


Reviewed by:
Dr. Caley Shukalek

Caley is passionate about evidence-based, patient-centred care, including telemedicine that can provide high quality care from wherever a patient may choose.

He helped create Alberta's PrEP guidelines and works as a specialist in General Internal Medicine with additional training in sexual health, including HIV and sexually transmitted infections.

He holds an Masters of Public Health from Johns Hopkins University, an MD from the University of Calgary and an MSc from the University of Alberta.