Allergic Reactions More Condition_symptoms How Are Allergic Reactions Actually Formed?

How are allergic reactions actually formed? - allergic reactions more condition_symptoms

Basically, I have a project about allergic reactions, and I know that he caued by antigens or allergens, but what really makes a person allergic to anything?

Specifically, the humans are caused allergic to bee stings, while person B is not it? Is there a particular function or something in the DNA, the immunity of a person or the overall strength of the immune system determined?