Delusions are mostly false beliefs rooted in the mind that seem real, but are not. Hallucinations are sensory-driven incidents that involve hearing or seeing something that isn't reality based. People with dementia or schizophrenia are prone to experiencing either delusions or hallucinations.
A person experiencing delusions often holds strong beliefs that may or may not be based on fact. For example, an individual may believe with certainty that everyone she encounters is spying on her and refuse to go outside because of the spies. Delusions can also come across to others as illogical or bizarre, even if based on factual truth.
Alternatively, someone experiencing hallucinations may hear voices in her head that speak clearly and seem real, which may lead the individual to act out in response to the voices. For instance, people suffering from mental illness sometimes do things after being instructed by one or more voices. Some people hallucinate visually and see people or objects that appear to be real.
Delusions and hallucinations are often frightening to the person suffering from them, as well as caregivers and casual observers. An appropriate way to deal with someone having delusions or hallucinations is to calmly validate what he is experiencing without being argumentative.