What causes loss of taste besides COVID-19?

What people call loss of taste is often reduced flavour because congestion prevents smells reaching the smell receptors. A common cold, allergies, sinus inflammation, or another nasal problem can do this. Dry mouth, gum disease, oral infection, smoking, some medicines, and nutritional problems may also alter taste. Less commonly, a head injury or a neurological condition affects the nerves involved. COVID-19 and Long COVID remain possible causes, but the symptom does not identify one diagnosis by itself.

Notice whether smell is reduced too, and record when the change began, recent infections, nasal blockage, new medicines, smoking, and mouth symptoms. Drink fluids and maintain gentle oral hygiene. Do not stop a prescribed medicine without checking with the prescriber. Arrange medical advice if the change persists, keeps returning, affects eating, or follows a head injury. Assessment may include an examination of the nose and mouth, medication review, and targeted tests.

Seek urgent help for sudden loss of taste with facial weakness, trouble speaking, one-sided weakness, severe headache, confusion, or difficulty breathing. Get prompt advice for mouth swelling, severe dental pain, high fever, dehydration, or inability to eat and drink. Persistent changes deserve review because treating the underlying nasal, oral, medication, or neurological cause may help.

Is my smell affected as well as taste? Could congestion, oral health, or a medicine explain this? Should I test for COVID-19? How long should I monitor the symptom before review?