CNS causes are brain tumour,aneurysm,hormonal disturbances,diabetes,multiple sclerosis
, zinc deficiency, malnutrition etc.Loss of taste
sensation can be due to nasal infections,flu,common cold, dryness of mouth, medications like antithyroid medications,rifampicin,gingivitis,vitamin B12 or zinc deficiency. You should consult a primary care physician. Based on your clinical examination findings he may further refer you to the concerned specialist. Treatment will depend on the underlying cause.