Insect bite or allergy, what's the difference?

Allergy to saliva: Great question. When insects bite us and inject their saliva, we have a reaction to this. The site can be a little red and puffy due to the bite itself, and then an allergic reaction at the site. Of course, if one has a severe bee allergy, e.g., there could be a dramatic, life-threatening reaction. Also, the insect pushes germs on our skin into germ-free areas, and that causes irritation too.