Anecdote. I heard about Milk Thistle when I was college, it supposedly protects your liver from damage. So I tried taking it when drinking, or immediately after drinking.
I was surprised that something so benign and unnoticeable during normal life could cause such a painfully upset stomach and aches in my gut area. It felt like being poisoned. I tried several times with different brands of milk thistle, too.
On the other hand, I took a low dose daily for a year and felt nothing untoward. No idea if it helped my hangovers, but it was a heavy drinking year that didn't result in that many hang overs. But I was much younger and relatively healthy.