There are some people who have allergic reactions to insulin.
This tended to be more common when insulin was prepared from animals and was not as pure as it is now.
The insulin currently used is mostly identical to human insulin.
Only very rarely are people allergic to the solutions in which the insulin comes.
Sometimes there is an allergy to the insulin molecule itself.
Generally the allergy starts by causing itchy feelings around the site of the injection.
Diabetic Coma
Paralumun New Age Village