I’ve been taking 3 of the 25 mg. oblong tablets for years with no I’ll effects. I take if for both my sinuses/allergies and at night to help with sleep (sort of).
Are you taking the brand name or a generic version of the capsules ? Different stores have their own branded generic versions.
Did you read the label to make certain that they are not a combo of some type. Some manufacturers (even brand name ones) come out with additional alternate combos for cough/cold or some other nonsense. If anything OTHER THAN Diphenhydramine is listed, that’s the tipoff.
The other pertinent difference is that the capsules vs. tablets have different filler/binder ingredients since the caps are powder inside the gelatin and the tablets are solid. These ingredients are supposed to be inert, but that’s not always the case and varies greatly from one manufacturer to the next and the only way to figure it out is trial and error.
Have you ever taken two of the tablets (50 mg.)? If you have and had no adverse effects, then you know it’s not dosage related. If you haven’t previously done that, that would be the first thing to try.
If you can take two of the tablets with no ill effects, then its definitely the filler ingredients (provided that both types of pills are from the same manufacturer, otherwise all bets are off).
I have no idea about the relationship with liver enzymes. Afaik, that’s not listed as a side effect of Benadryl, per se, as it would have been discovered long before now since its been around for half of forever. Benadryl is as old as dirt, practically :)