Anosmia

Anosmia is the loss of sense of smell, hyposmia is a reduced sense of smell.https://www.hopkinsmedicine.org/health/conditions-and-diseases/smell-and-taste-disorders A change in sense of smell may occur alongside a change in sense of taste.

ME/CFS
This is not a symptom typically reported in ME/CFS.

Causes
Common causes include
 * obesity
 * diabetes,
 * hypertension (high blood pressure)
 * poor nutrition
 * nervous system diseases, e.g., Parkinson's disease, Alzheimer's disease, or multiple sclerosis
 * colds, flu or flu-like illnesses, sinus problems and allergies
 * some scientists have found altered or loss of smell and taste linked to COVID-19 illness in some patients

Learn more

 * Smell and taste disorders - John Hopkins University