The histamine blockers being used for long-haul treatment are over the counter, like Pepcid AC (H2 blocker) and Claritin (H1 blocker)--not prescription strength. I don't know if that makes a difference in contraindication in seniors, as you mention? I've never heard about the contraindication before, nor seen it mentioned on other message boards. Do you know the reasoning behind it, in seniors?

This is a really good explanation for why the histamine blockers work, as many people with long haul have symptoms very similar to MCAS (mast cell activation syndrome) - https://hoffmancentre.com/treatments-for-lowering-histamine-and-reducing-mcas-symptoms/ & https://hoffmancentre.com/treatments/mcas/