Olfaction: Disorders

We live in a sea of volatile molecules whose presence we are aware of largely or exclusively through our sense of smell. Smells warn us of environmental dangers (fire, toxic chemicals); they create a sense of intimacy with loved ones, whose signature odors we learn to recognize; they provide pleasure through perfumes and other desirable fragrances; and they constitute a substantial proportion of the flavors of food, as volatile molecules released in the oral cavity flow through the nasopharynx to the nose and stimulate olfactory receptors. Because changes in smell greatly disrupt the ability to appreciate food flavors, eating becomes a dissatisfying experience, and the many social occasions that center around food can become awkward and frustrating. Moreover, the inability to detect leaking gas or burning or spoiled food creates real dangers in daily life. Few people appreciate the range of information about our world provided by the sense of smell, or contemplate the impact of a disruption in that source of information. Yet, as demonstrated in this entry, olfaction is a vulnerable sense, and olfactory dysfunctions are common.