Friend had oysters yesterday, felt bad in afternoon, had hallucinations that night. causes/concerns? even though better now? should have hospitalized?

Not Necessary: I am happy to hear that your friend has recovered from what was likely either mild food reaction vs food poisoning, depending on his or her personal history. Hallucinations can be caused by fever, among other things. I recommend to all members that you write in for your concerns only, and suggest your friend do the same or be seen in-person should they have a recurrence of their symptoms.