Yes, it’s possible to get an STD from receiving oral sex without a condom or dental dam. Herpes can be easily spread from one partner to another during oral sex because it’s passed through skin-to-skin contact and not just fluids. Other STDs, like gonorrhea and chlamydia, can infect the throat. It’s also possible to get or pass on syphilis, hepatitis B, and HPV this way.
Best way to avoid all that? Use a condom or dental dam during oral sex and get tested regularly.