Acquired anosmia describes the loss of your ability to smell. It results from damage to the first cranial nerve and olfactory bulb. It is a common early symptom of Superficial Siderosis with a long slow progression. Most people will notice distasteful odors or phantom smells at first. Over time, the dysfunction of your olfactory receptor neurons leads to the complete loss of your sense of smell.
The sense of smell controls your concept of the more delicate qualities of taste. When you have anosmia, you can still distinguish salty, sweet, bitter, sour, and umami from the taste buds located on your tongue. When you lose your sense of smell, you lose the ability to enjoy the nuances of flavor. Eat chocolate ice cream with your eyes closed. A person with anosmia will tell you it’s cold, sweet, soft, and creamy, but they are unable to tell it’s chocolate.
The first cranial nerve is responsible for qualitative odor sensations like flowers or fresh-cut grass. The fifth cranial nerve controls the overtones of smell like warmth, coolness, sharpness, and irritation. An onion or ammonia will not only smell strong but will also cause a body response. For example, when a person inhales a cut onion deeply, tears will form.
Even if you progress to complete anosmia you will still be able to distinguish stinging, burning, cooling, and sharpness through the nerve endings in your tongue. Dysfunction of the fifth cranial nerve that connects to the tongue is extremely rare. The combined loss of both taste and smell is called ageusia.