Q. I quite like giving blow jobs and usually swallow. Is it bad for you health-wise to swallow semen?

A. It's not 'bad' for you: semen is mostly water and mucus, though there are traces of acids, salt, chloride, ammonia, calcium, carbon dioxide and cholesterol (sperm makes up a mere one per cent of ejaculate). But the only problem is a large one: if he carries an STI, you may get it. Take your pick from a long list of diseases that can be passed on this way. In fact, just wrapping your mouth around his penis puts you at risk of contracting herpes, syphilis or genital warts if they're present. If you want to be truly safe, make sure you use a condom during oral sex.