Taste and smell in disease (second of two parts).

Disorders of taste and smell are common occurrences that can lead to modifications of dietary habits that may in turn exacerbate disease states or nutritional deficiencies. In addition, they are often nagging problems that diminish the quality of life. Such disorders can result from a range of disease states, pharmacologic and surgical intervention, aging, radiation, and environmental exposure. A search for the pathogenetic mechanism should include the determination of possible (1) local injury from physical or chemical causes, (2) damage to neural projections, (3) disturbance of the cycle of regeneration of chemoreceptors resulting from general malnutrition, disease agents, metabolic disturbances, drugs, or radiation, and (4) alteration in the saliva or fluids bathing the olfactory mucosa by drugs or metabolic agents. Viral infections, normal aging, head injuries, and nasal obstructions are the most common causes of smell disorders. Drugs are common offenders in taste dysfunction. Chemosensory disorders frequently remit when concomitant medical conditions are treated or offending drugs removed, although full recovery may take several months. Considerable research is now under way in this area, and it is to be hoped that we will soon have a better understanding of how to diagnose and treat these common disorders.