A wasp uses its sting for killing prey, but it can also use it very effectively as a defensive weapon. The sting has associated glands which produce venom.
A hornet sting can be very painful, but is normally not dangerous, as the amount of venom injected is very small. In some cases, however, people do become ill after being stung by a hornet. This is due either to the venom being injected directly into a blood vessel or to the victim being hypersensitive to one or more of the substances contained in the venom. A sting in the mouth or on the neck can be serious, as the mucus epithelium may become very swollen, making it difficult for the victim to breathe. An ordinary uncomplicated sting can be treated with ammonia or alcohol or with a cold poultice, followed by an antihistamine ointment. If the victim becomes pale and feels unwell with giddiness and nausea it is advisable to seek medical advice immediately.