People exist who are toxic to me and not to most other people. Just like foodstuffs exist that I’m allergic to and most other people are not. (Nutmeg! Almost any amount of nutmeg, even too little to taste so I know it’s not just a strong dislike of the flavour, makes me queasy. Too much nutmeg, meaning the amount that used to be normal on vegetables in Dutch nineteen-seventies cuisine, gives me interesting hallucinations but also makes me vomit.)
Thinking about having certain people rub me the wrong way, when they aren’t actively being evil or doing anything wrong, as an allergy helps me tremendously in dealing with them. I can just shrug the rubbing-the-wrong-way off until the exposure becomes too much and I want to avoid their presence as soon as I can (immediately isn’t always possible, of course) and stay away for a while. Fortunately this is the kind of allergy that’s no more than an annoyance (sometimes major, granted), not likely to cause potentially fatal anaphylactic shock.
I actually have to interact with a toxic person for the reaction to manifest, but it doesn’t have to be directly: sitting on the same train, in one another’s sight, can do it, even if we have never met before. But walking in the same crowd, for instance in the book market, usually doesn’t. I do get acute too-many-people overload from crowds at times that makes me want to get to a quiet place RIGHT! NOW! but that’s not the same thing.
And there are people I dislike for some specific reason, but that’s not the same thing either. If I’m “allergic” to a person that might cause dislike, but it’s seldom the result of dislike for another reason. For what it’s worth, the people I dislike most often are those who claim authority in field X because they’re important in field Y, “I’m such a good surgeon, of course you have to listen to me when I tell you how to read the Epistle!”