A: Humans are really an interesting bunch. We can mimic so well. And we have all said from time to time that a part of me wants to do so and so, but another part really wants to do this other thing instead. Now everyday individuals say that and understand that to be just a part of them, a part of the whole. Individuals who have managed to give these parts a more "real" identity have in fact created a new personality with its own patterns, rules, and beliefs.
There was an earlier question I answered that dealt with simultaneous and sequential incongruence. Individuals with Multiple Personality Disorder or MPD are in fact very congruent in each personality, like a great actor committed to a specific role. In most cases, new identities are the result of incongruent parts forming their own congruent identities. And whereas most people seek integration for balance, their system keeps dividing or separating to obtain balance.
And there is another remarkable feature of the human system; to preserve a certain level of ecology, each identity creates its own patterns and behaviors. This is one way each identity distinguishes itself from the other. Each one can say, "Well, I don't do that, he or she does." Each identity takes responsibility for only its part, not the whole.
So going back to your question, yes each personality or in some cases a group of personalities will share a particular response or behavior while the others will not. There have been cases where one personality had diabetes, and the other personalities could produce insulin without any problem. Some have gotten scars or marks that disappear with other personalities. And even allergies switch from personality to personality.
And to further answer your question, an allergy is basically a mistake in recognition at the level of the immune system. If someone gives you a compliment and you perceive it as an insult, you will respond to the remark as an insult. That is all the immune system is doing.
The immune system perceives food, bees, pollen, dust, and other typical allergy-inducing things as a danger to the system. And the response is better known as an allergy-response. Structurally this is the pattern of any allergy. Using NLP, you can retrain your immune system to respond in a more appropriate way. You could do it yourself or with the help of a professional. However, if you do try to do it yourself, please take all the necessary precautions. Each immune system is different and each person's allergic response is different as well.
Some resources available to assist your understanding: the movies Sybil and Identity. Also read the book Heart of the Mind by Connirae and Steve Andreas.
-Oz