The only prescription antihistamine I have ever tried is Atarax (Hydroxyzine) and it was for itchy hives. It completely knocked me out. I slept for many hours, more than normal, then woke up and went out briefly but I was still very groggy and I went back home and slept more. It was pretty awful. I ended up cutting the tiny tablets into four pieces, and taking one fourth the dose to try to deal with the hives without getting knocked out.
I have a similar reaction to Benadryl, which is a non-prescription antihistamine, usually used for runny nose and itchy eyes caused by colds or allergies. If I take it before bed it does help me fall asleep but I feel like a zombie the whole next day. It's pretty terrible and I avoid it.
I would not consider taking any antihistamines for this reason.