Olfactory hallucinations are sensory experiences where a person smells odors that are not present in their environment. These smells can be pleasant or unpleasant and may vary from person to person. They can occur due to various reasons, including neurological disorders, mental health conditions, or as a side effect of certain medications. Common causes of olfactory hallucinations include Parkinson's disease, schizophrenia, and temporal lobe epilepsy. In some cases, they may also arise from exposure to toxins or infections affecting the nasal passages. Understanding the underlying cause is essential for effective treatment and management of these hallucinations.