Hallucinations and delusions are common occurances in someone who has Alzheimer's disease. It's best to really understand what they are. First, hallucinations are seeing things or hearing voices when there's nothing there. These are real experiences and you can't talk someone out of them. You frighten them more if you try to do that. Delusions are false ideas. A common one is the belief that someone's taking your things. The best thing to do when you notice someone having these experiences is to reassure them, not to argue with them. So for example, if they say, "I see a frightening animal in the corner," just say, "I'll keep you safe, let's leave the room," instead of, "I don't see it." In some cases, you can reassure and distract persons away from these and they'll calm down. But when they persist, and they're very distressing for persons who are experiencing them, it's important to tell your doctor because there are medications that are effective and can help substantially.