In strong opinion should not swallow or drink sperm for the following reasons:
First: The act allows the ingestion of something unclean like madhi, wadi, or urine.
Secondly: Mani is a mustakhbats (disgusting), so the scholar who says it is holy also thinks it should not swallow it, because the word of allah:
وَيُحَرِّمُ عَلَيْهِمُ الْخَبَائِثَ .الأعراف: 157
Meaning: "And he (Prophet sallallaahu 'alaihi wasallam) forbade the things that khabits (very dirty / ugly)" (Surat al-A'raaf: 157)
Said An-Nawawy rahimahullahu:
هل يحل أكل المني الطاهر؟ فيه وجهان: الصحيح المشهور أنه لا يحل لأنه مستخبث
Can swallow the sacred semen? There are two opinions, and the right and famous that it is not lawful because of mustakhbats (disgusting) "(Al-Majmu '2/575)
Third: Some health experts say that in medicine it turns out this act if done repeatedly will be dangerous because the live semen can injure the stomach wall resulting in bleeding in the stomach