Question: What exactly does it mean to be allergic to an insect sting?
Answer: Being allergic is having an abnormal sensitivity. So being allergic to stings means that someone has been sensitized, that means they've developed allergic antibodies in their system that can make them react abnormally to a sting. So being allergic to stings means having an abnormal reaction.
A normal reaction is itching and pain and swelling. Swelling can be an inch or two in size and that's in the normal range. Some people have sensitive skin and can get larger than average swellings, but that's still not really abnormal.
An allergic reaction, being allergic means having a more extreme reaction. And there are extreme large swellings that can happen that can even involve the whole arm or leg. And there are internal allergic reactions like throat swelling, trouble breathing or dizziness or unconsciousness.
And of course the treatment is different for each of these reactions as to whether there's a need for special medicine for the swelling or emergency treatment for the more extreme and dangerous reactions.