Oral sex is not risk-free. Infections that can be transmitted through oral contact include gonorrhoea and chlamydia (which can infect the throat), herpes (oral-to-genital and vice versa), syphilis, and HPV. HIV transmission through oral sex is possible but considered low risk compared with other routes.
Throat infections from gonorrhoea or chlamydia often cause no symptoms, so they can be missed unless specifically tested for with a throat swab. If you have oral sex with new or multiple partners, mention this to your clinician so the right sites are tested.
You can lower the risk by using condoms or dental dams during oral sex and keeping up with vaccinations such as HPV. If you have a sore throat, mouth ulcers or any genital symptoms after oral sex, see a licensed doctor or sexual-health service for assessment and the appropriate tests.