Just make sure your anti-histamine is not in this list of drugs to avoid.
I asked the pharmacist for a drowsy antihistamine the other day and they gave me something from behind the counter (no script required). No idea if it was anticholinergic: most drugs require compromises so if something works better for sleep for me I'll judge the risks for other side-effects.
Normally I use a loratidine if I wake in the early hours and that usually gets me back to sleep, even though it is non-drowsy.
I wanted to try a different antihistamine to see if it worked better: jury's out on that at the moment.
Personally I think it is very important to experiment on yourself, and test a variety of solutions. I will even test alternative medicine for important problems. I strongly avoid dangerous solutions. I am fairly conservative and I especially dislike taking pills, but I believe in the value of trying a bit of science on your problems.
If you need something for sleep I highly suggest you either try melatonin if you want something OTC or talk to your doctor for something that requires a prescription.
Aside from melatonin, pretty much every OTC sleeping drug you can get is an anticholinergic drug which is better to avoid.
Yes Promethazine (the anti-histamine I'm using) is a moderate anticholinergic.
AFAIK Melatonin needs a doctor's prescription in New Zealand.
I will balance the risks as best I can (lack of sleep is also very unhealthy!!), and keep scientifically trying softer alternatives.