Sexually Transmitted Infections (STIs)
Sexually Transmitted Infections (STIs) are common and can be passed on during sex or through sexual contact. More than 30 different bacteria, viruses and parasites are known to be transmitted through sexual contact.
Some of the most notable ones include gonorrhoea and chlamydia (bacteria), trichomoniasis (a protozoan), hepatitis B, herpes simplex virus, HIV and Human Papillomavirus (HPV).
Many of these infections have no symptoms, which increase the likelihood of these diseases being passed on.
Some of the symptoms which may present in men and women include:
- An unusual discharge from the vagina, penis or anus
- Painful urination
- Lumps or skin growths around the genitals or anus
- A rash
- Unusual vaginal bleeding
- Itchy genitals or anus
- Blisters, sores or warts around the genitals or anus
- Warts in the mouth or throat (though this is rare)
If an STI is suspected, its best to get tested at a sexual health clinic. Bear in mind some STIs can take up to 7 weeks after having unprotected sex to show up on a test.1 Most STIs need treatment. The treatment recommended will depend on which STI is detected.
The vaginal microbiome environment has been found to protect against STIs in a healthy state (a state dominated by lactic acid producing lactobacillus). Specifically, Bacterial Vaginosis (BV) has been found to be an independent risk factor for acquisition of STIs.2
References
- NHS. Sexually transmitted infections. Available at: https://www.nhs.uk/conditions/sexually-transmitted-infections-stis/. Accessed Mar 13, 2025.
- Wiesenfeld HC, Hillier SL, Krohn MA, Landers DV, Sweet RL. Bacterial vaginosis is a strong predictor of Neisseria gonorrhoeae and Chlamydia trachomatis infection. Clin Infect Dis. 2003;36(5):663-668.
