It just might be that the first type of chemical warfare occurred about 2,400 years ago. Would you believe the agent was honey? A Greek army was inadvertently poisoned because of eating local honey about 400 B.C. They eventually recovered but later around 69 B.C. honey was used to poison a Roman army and King Mithridates was able to repel the Roman attack.
A group of neurotoxins named after Asa Gray, the father of American botany, is known as grayanotoxin. This substance can be found in a group of plants in the family Ericaceae. If bees gather nectar and pollen from these plants and if the subsequent honey contains a high concentration of grayanotoxin, those eating the honey have been known to become ill with multiple symptoms which are serious and sometimes life threatening.