Histamines are inolved in any and all "places I gotta scritch?" Specifically, scabs and under casts?

This is a spinoff from suggestions of topical and even systemic use of Benadryl, etc., in []My dog has a hot spot and I don’t want to put a damn cone on him. Advice?](https://boards.straightdope.com/sdmb/showthread.php?t=860241)

I talked about that thread, and sections on local anesthetics in of another related one, Is Nitrous Oxide (Laughing Gas) actually an anesthetic, rather than a “relaxant”?, with my podiatrist who had to excavating not for a mind but a deeply embedded splinter which turned out be non-existent. (Go SDGQ!)

I’m sort of familiar with histamine response and mast cells due to bad allergy asthma (from that same silly dog, BTW).

But help me–

1: the skin irritation-you-want-to-pick-at/scratch of scabs, is that itchiness a histamine reaction? Ie, if it itches it’s histamines, even though it’s not to me, an allergic response but something that feels creepy crawly, sort of, because of skin tightness or something?

2: same question, with different circumstances, for the famous crazy itching under a hard cast over a broken bone:
2a: not a scab pulling tight, but perhaps because the skin hasn’t been stimulated whatsoever, and it’s sending signals that that not’s a good thing?

Empirical evidence from my dog–where actually I’m starting, despite this OP, with Benadryl cream, because I already have it, not an over-the-counter Lidocaine prep, is not in yet.

2b: that too, doesn’t strike me as what I understand to be a histamine thing.

ETA: I’m more comfortable understanding the under-the-cast itching involving histamines, and the benefit of anti-histamines for that.

Not sure why, though. All sorts of skin conditions which I, for one, have never heard described as allergic responses respond massively to anti-histamines.