Plants defend themselves against predators, including man. There are obvious defences such as stinging nettle-like strategies, and burning or blistering latex resins. Others use different methods to incapacitate. They include gastrointestinal distress (vomiting or purgation), blindness, neurological disability, or even asphyxia. This clearly illustrates the ingenuity of plant chemistry which, while daunting, has led to some rather extraordinary discoveries. The poisonous potential of numerous plants coincides with a medicinal effect that cannot be ignored. What is the difference between a poisonous, edible or therapeutic effect?