Personally, I don't take any 1st generation antihistamines. They are VERY triggering for me. I only take 2nd or 3rd (mainly Zyrtec and Allegra). I would not take midol as the pyrilamine is a 1st gen and would make me loopy.
Long story short and I won't bore you here....but one of my worst relapses started with benadryl while spending a spring in SC. Pollen everywhere and I foolishly thought I could "just take an OTC allergy med". As innocently as I did that, it was horrible for me. I learned the hard way and I am VERY CAREFUL now about what chemicals go in my body.
Here is a link to looking at the different classes of antihistamines. I learned this page and can safely take the newer class of them when indicated.
https://en.wikipedia.org/wiki/H1_antagonist
I am not a doctor and am not giving medical advice per se. All I would say is do your due diligence before taking ANYTHING.