Why does a leech start dying the moment salt touches its body? This video explains why a leech almost instantly collapses when it comes into contact with salt. What looks like a simple reaction is actually a brutal biological process driven by basic physics and cell biology. A leech’s body is made up of approximately 80–90% water. When salt touches its skin, it triggers a process called osmosis. Salt creates a high-concentration environment outside the leech’s body, forcing water to rapidly move