Doctor listed Benadryl tablet "as needed" but is still taken everyday. How effective is it?

If they have early Parkinsons, did the MD recommend it to reduce tremor or as a sleep aid? Most over the counter sleep meds use diphenhydramine aka Benadryl. The wine: one glass won't do much. Consider that most cough syrups have an antihistamine and alcohol.
But if they are taking more than one pill and more than one glass of wine every night, there's a good possibility they have been doing this for a while and need more to overcome a tolerance.

The wine/Benadryl combo is obviously being used as a sleep aid - I would think there's a safer route to take than this. That said - my son who is severly autistic had been taking a 3mg meletonian every night for sleep since toddler age, he is now almost 23. I would have thought he would have developed a resistance to it by now but he hasn't. Once in a while I'll hear him up and puttering around in his room past the time he is usually asleep and sure enough I'll realize I had forgotten to give him the pill. In his case it's impossible to be a "placebo effect" as he doesn't understand what the pill is for. On the other hand, I've been taking pain meds for a back issue for about 15 years and every few years the dosage has to be up'd because of a developing immunity. It's hard to say for sure unless you can get your parent to stop the pill or switch it out for something else to test how effective it really is. And of course, it would be a good idea to talk about this with your parents doctor.