What causes nausea after swallowing semen?

Feeling nausea after swallowing semen is not due to a physical or medical condition, but rather a psychological condition. It's called conditioned taste aversion

Answer:Swallowing semen can upset the stomach as it contains enzymes that interact with mucous membranes. These enzymes help to facilitate successful fertilization in the womb, but they can also affect the mucous membranes of the digestive tract when swallowed and cause indigestion and stomach pain.