While it would be rare to become infected from having oral sex with someone infected with HIV/AIDS, we do know that transmission is through body fluids. If the infected person had bleeding gums or a mouth sore, blood may be transmitted to the partner’s mucus membranes.
My advice is that you wear a condom during oral sex (assuming you are male). For females having sex with females, the use of dental dams or plastic wrap will aide in prevention of sexually transmitted infections.
The CDC has a great web site on HIV transmission. I have included the web address: https://www.cdc.gov/hiv/resources/qa/transmission.htm
Hope this helps!
The FNF Experts