Q & A | Swallowing Semen

My boyfriend wants me to swallow his semen.. Is that dangerous?
Ejaculating into a partner’s mouth is a common practice during oral sex/fellatio. In a safe situation (where there is no danger of catching an STD), the semen-receiving partner may choose to spit the semen out, or to swallow it.
Before you engage in fellatio, I’d recommend that you and your partner both get tested for sexually transmitted infections (STIs). If not, please use barriers for oral sex and abstaining from making contact with ejaculate.
Semen is mostly water, but also contains amino acids and protein, sugars such as fructose and glucose, minerals such as zinc and calcium, vitamin C, and a few other nutrients. Sperm cells themselves make up less than one percent of semen. Semen is edible, and if swallowed, will travel down the esophagus and into the stomach, where it will be digested in the same way that food is. You can never get pregnant by swallowing semen.
Some people accept the taste of semen, but others complain that swallowing semen can give them an upset stomach. In rare cases, you may have an allergy to the proteins found in semen.
What does It Taste Like?
The taste of semen varies. Bitter, sweet, metallic. So, one may expect to find the taste of semen anywhere from enjoyable to tasteless to disgusting. But there is a way of controlling the taste of semen, which is through diet. Keep track of the diet, and communicate with the partner about when it tastes better or worse.
Foods that can improve the taste of semen include: pineapple, cinnamon, lemon, or green tea. Finally, you could also use a sweetened lubricant to try to mask the taste of the semen, or wear a flavored condom so there is no contact with the semen at all.
Some more information for you:), Semen usually has the body-temperature, and is thick like motor oil and with the density of milk. Volume is between 2-5 ml per ejaculation.

Does Swallowing Semen Really have Health Benefits?
Semen also contains more than 50 different compounds including hormones, endorphins, neurotransmitters and immunosuppressants. Other substances present in the semen include the following:
fructose
ascorbic acid
zinc
cholesterol
protein
calcium
chlorine
blood group antigens
citric acid
DNA
magnesium
vitamin B12
phosphorus
sodium
potassium
uric acid
lactic acid
nitrogen
vitamin C
Also present in the semen are mood-enhancing compounds such as cortisol, estrone, oxytocin, thyrotropin-releasing hormone, prolactin, melatonin and serotonin.
Here are ten alleged health benefits of seminal plasma:
1. Natural anti-depressant.
2. Natural anxiety reducer.
3. Improves quality of sleep.
4. Increases energy.
5. Improves concentration.
6. Improves memory.
7. Improves mental alertness.
8. Assists with pregnancy maintenance.
9. Increases female-initiated sexual behavior.
10. Reduces pain.

On the other hand, there are possible disadvantages of consumption of semen
Semen *can* contain several viruses that may be transmitted via bodily fluids from an infected man.

Source: Q & A | Swallowing Semen