Insects whose stings could cause allergic reactions in some people belong mainly to the order of Hymenoptera i.e. Bees and Wasps.
Bees are not naturally aggressive. They sting only when they feel threatened or when their nest is in danger.
A bee‘s stinger is barbed and cannot be withdrawn when the skin is penetrated - a real miniature harpoon! In the bee‘s struggle to escape, the stinger, poison gland, and some of the digestive tract are torn from its body, so the bee dies.
Wasps, (ordinary wasp and hornet), on the other hand, are naturally aggressive. They are particularly aggressive in the autumn, when their food runs out.
A wasp‘s stinger is smooth (non-barbed) and can be easily withdrawn. A wasp therefore can sting again and again.