Thanks for providing more information.
I understand your concern.
And as you describe chances of any sinus related issues are less likely in your case.
And the sense of taste and smell are intimately related to each other and usually the loss of one sensation results in loss of the other sensation as well.
There are few important possibilities which should be investigated and can be responsible for loss of smell & taste such as
neurological manifestations (brain growth or mass), neuropathies, vasomotor rhinitis, long standing GERD related complications,Gingivitis or gum disease,Sinus infections or nasal polyps,Vitamin B12 and Zinc deficiency,Diabetes, Hypothyroidism, Drug induced and most likely drugs are antihypertensives, antihistaminics, anticonvulsants, antidepressants, antibiotics.
Further blood work like complete blood count,blood sugars, thyroid tests and investigations like CT/MRI of the head and sinuses should be advised.
MRI can also help in detecting any neurological pathology so you can consult a neurologist for further evaluation and management.
In the meantime zinc and vitamin supplementataion helps restore both taste and smell to some extent so you can take zinc lozenges once a day as well as multivitamin containing B 12 once a day.
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