Olfactory hallucinations can be important indicators of underlying health issues. In some cases, phantom smells may result from sinus and respiratory issues, like sinusitis and nasal polyps, which can disrupt air and mucus flow in the nasal passages, leading to an altered perception of odors. It can follow a severe respiratory infection, such as COVID-19, according to Mayo Clinic. It can also be brought on by dental problems (per Cleveland Clinic).
The study in Continuum states that phantosmia is a common symptom of a head injury that has damaged the olfactory nerve or the olfactory cortex, which is responsible for processing smell. Additionally, phantosmia can be associated with various medical conditions, including Parkinson’s, Alzheimer’s, multiple sclerosis, and epilepsy. It can also be a side effect of certain medications, such as antidepressants and anticonvulsants.
According to a 2022 report in Frontiers in Behavioral Neuroscience, psychological factors such as stress, anxiety, and medication can also influence the perception of phantom smells, as emotional and psychological distress may cause the brain to misinterpret sensory data, resulting in olfactory hallucinations.