You have said that, "A person who is highly allergic to something usually craves what he is highly allergic to." But then you ask: "How can one body crave what creates conflict and destroys it?" Many people suffer allergies without the knowledge or means to really help themselves. Some of us can't always afford to choose "healthy" foods. Perhaps you have some words of encouragement to those who suffer from allergies?
Just because there is no easy way to find and eat foods that are not corrupt is never an excuse to eat foods that are. It is better to go without eating something that harms us, than to ingest what weakens the immune system. And the reason we don't know this is true, or practice its truth -- in spite of having to suffer for our conviction -- is because we don't practice (as we should) this same understanding with our own harmful, soul-corrupting negative thoughts and feelings.
We "eat" what we do (inwardly or outwardly) because we find pleasure in those "foods." Now this isn't to say that one doesn't have natural allergies that drain (to an extent) one of vital energy in their attack on the system. But, here again, we may find that we are complicit in this negative condition, because we go out and eat lifeless foods that leach the body of its recovery abilities.
The main point here is that just as we are "addicts" of our own desire-driven thoughts and feelings, so we are driven to take into our bodies food stuffs that make us sick. And if it's my hand that lifts the fork to my mouth, then who am I to blame for the illness engendered by that action?
As for encouraging words, here's a few: It is our right to be conscious of whatever compromises us, and that this awareness -- in itself -- will not only separate us from what harms us, but help to heal us at the same time.