Q. Is ejaculation in the mouth safe? If my wife swallows the liquid I ejaculate in her mouth, will it cause any disease or any problems? Right now, I don't ejaculate in her mouth as she's worried it will be harmful for her.
A. As long as both you and your partner have a clean bill of health, drinking cum is safe and even somewhat nutritious. A one gulp serving - generally measuring between one to two teaspoons - usually contains hundreds of millions of Sperm, as well as a huge list of ingredients, including: water, fructose and proteins (see Male Ejaculation for the entire spiel). At less than fifteen calories per load, ejaculate is non-toxic and safe to ingest - even in larger quantities, as in Bukkake.
To further clarify the safety aspects of swallowing ejaculate, we need to discuss Safe Oral Sex. If a person has open sores, cuts, or abrasions, there is a chance that an STD/STI such as herpes, HPV (human papilloma virus), gonorrhea or syphilis can be contracted through oral/genital contact.
However, as long as you and wife are disease free, you can enjoy the wonderfully gratifying sensation of cumming in her mouth. However, make sure that her concern for safety isn't just a veiled way of avoiding the act itself. Whether a person swallows or spits-out is entirely a matter of choice, and her preference to do one or the other should be respected.
Reassure her that your semen is safe to ingest, but make sure you avoid putting undue pressure on her to do an act she'd rather avoid or avoid talking to you about. Not wanting to swallow your ejaculate might indicate a few things: one, your tastes unpleasant (check out Cum Tastes Yucky); two, it triggers an unpleasant gag reflex; or three, she has a psychological or emotional reason to avoid it (e.g. it makes her feel uncomfortable). Whatever the reason, try and talk to her about it; if she's willing to share her reasons why, great; if not, get used to keeping a tissue box by the bed.