Poisonous saliva of leeches

Terrible leeches live in the quagmire. They have nasty blue skin with swollen veins, tiny ugly eyes and a disgusting round mouth with small sharp teeth. When they see an enemy, they spit poisonous saliva at him, leaving unhealed scars on the skin... Please bring me this saliva, and I will try to make an ointment that helps from burns.