I recall in high school telling a fellow friend that every time I took Tylenol pm I dreamed of scifi space shit.

So she took one. And told me the next day she also dreamed of aliens. But the alien was a basketball player. And they started dating.

That was 25 years ago. I still remember that fun adventure of discovering benadryl.

Also it’s likely it causes vivid dreaming because it suppresses rem. Alcohol can do the same. But when it wears off, your body tries to compensate for the loss by having more REM. If you are still asleep , you get that effect.

Benadryl has a pretty short half life. So. Yep. That’s probably the mechanism.

For me. It’s still usually scifi related themes but I consume a lot of scifi fiction. So.