When you’re giving it:
It is theoretically possible to get HIV from giving head but the likelihood of this occurring is very low. No one knows exactly how risky it is, partly because most men who do it will also have other forms of sex as well and it is impossible to know which sexual act is responsible for the transmission of HIV.
The reason that oral sex is so much safer than anal sex is that the throat is not as vulnerable to infection as the rectum is. Saliva has properties that can disable some infections, including HIV, and so there needs to be quite a lot of HIV present for infection to take place. Also, the mouth and throat are not as efficient at absorbing liquids into the bloodstream as the lining of the rectum is. Even if you swallow cum, any HIV that may be there will usually be killed by the strong acids in your stomach.
Although the risk of HIV infection is fairly low, some other STIs can be easily passed via oral sex, such as chlamydia, gonorrhoea, herpes or syphilis. These risks can be avoided by using a condom for oral sex.
There is a chance of picking up hepatitis B through oral sex, if you have not been vaccinated. If you have an existing STI in your throat you will be more vulnerable to infection and the chances of picking up HIV or Hep B are increased.
When you’re getting it:
No one has ever caught HIV from getting head. However, you may be vulnerable to other STIs this way, such as chlamydia, gonorrhoea, herpes and syphilis. This is because all of these STIs are much more infectious than HIV.
If you wanted to prevent the chances of getting an STI you should wear a condom for oral sex. As most men choose not to do this, it’s advisable to have a regular sexual health check-up to ensure that any infections you may pick up can be detected and treated quickly.