Loss of taste and smell can occur due to sinus infection, common cold, nasal polyps, aging and exposure to certain medications and toxins, states the Mayo Clinic. It can also happen because of Alzheimer's disease, Parkinson's disease, radiation treatment, dental problems or injury to the nose, head or face.
Additional causes of the loss of smell and taste can be allergic reactions and breathing in air of poor quality, explains WebMD. Poor air quality leads to greater exposure to pollutants and toxins in the atmosphere.
Losing the senses of taste and smell can also occur if there is injury to the nose, head or face, reports WebMD. If the olfactory nerves are damaged during surgery, it can lead to loss of taste and smell. Radiation treatment administered for treating head and neck cancers are other potentials instigators, as are medications such as antibiotics, anti-inflammatory drugs and medicines for heart diseases and depression. The presence of nasal polyps, which are non-cancerous growths that block the sinuses and nasal passage, can also lead to the loss of taste or smell.
The sense of smell and taste can also be lost due to some medical conditions, such as Parkinson's disease, Alzheimer's disease, congenital diseases, multiple sclerosis, nutritional deficiency and hormonal imbalance. Smoking and cocaine abuse are risk factors as well, notes WebMD. To an extent, the sense of smell and taste can be lost due to aging, particularly after 60 years.