Allergic reactions actually come from a simple misjudgment the mind made once when it encountered an unknown substance like ragweed or cat dander. Since the mind controls everything the body does, the mind ordered a histamine reaction to what it thought was a threatening bacterial substance.
At a conference, I was having dinner with a few of the attendees at an old Route 66 style burger and malt shop where we were told we HAD to try the malts.
A lady at the table was quite upset because she was lactose intolerant and her condition had gotten worse over the years. I worked with her for about 10-15 minutes right there at the table. She enjoyed a large vanilla shake with dinner, and she felt fine afterwards. I checked with her later that evening and again the next day. She felt fine. She was no longer allergic to milk products. Her mind had reclassified milk as a safe substance for her body.