.......they are always protecting their hive from dangers; that is their instinct. Once they can sense any threats, they would always attack any animals and even humans who are near their hive. And the worse thing is that, they always attack in hundreds. These insects are very sensitive that anything strange to them, they would always consider it as threat to their safety.http://animals.nationalgeographic.com/animals/bugs/hornet/
.....some people are allergic to their venom and can have very dangerous reactions to a sting. ........Tony Quah, the climbathon & trekking sifu said : " Do bring along anti-hisatimine while hiking as this is my practice to take these pills for all my hikes just for precautions "
This is great idea, precaution, prevention, and prepareness is the way to go.