Smell Disorders

By Tim Taylor

What do you smell?

Specialized sensory cells

Download this episodeA person’s ability to smell comes from specialized sensory cells called olfactory sensory neurons found in a small patch of tissue high inside the nose. These cells connect directly to the brain. Each olfactory neuron has one odor receptor. Microscopic molecules released by substances around us, like freshly baked bread, stimulate these receptors. Once the neurons detect the molecules, they send messages to your brain, which identifies the smell. Smells reach the olfactory sensory neurons through two pathways, through your nostrils or through a channel that connects the roof of the throat to the nose. Chewing food releases aromas that access the olfactory sensory neurons through the second channel. If the channel is blocked, such as when your nose is stuffed up by a cold or flu, odors can’t reach the sensory cells that are stimulated by smells. As a result, you lose much of your ability to enjoy a food’s flavor. In this way, your senses of smell and taste work closely together.

Damage to nerves

Download this episodePeople with smell disorders typically either have a decrease in their ability to smell or they may have undergone changes that affect the way they perceive certain odors. Hormonal disturbances and sinus and other upper respiratory infections can interrupt a person’s sense of smell. Certain medications, such as blood pressure medicines or certain antibiotics, can change or decrease a person’s ability to detect odors. Loss of smell can also be caused by blockage caused by nasal polyps, nasal septal deformities or nasal tumors. Smoking is the most concentrated form of air pollution that most people are exposed to and can impair a person’s ability to identify odors. A head injury or virus can sometimes damage the nerves related to smell. Radiation therapy patients with cancers of the head and neck often complain of a lost sense of smell. Conditions that affect the nervous system, such as Parkinson’s disease or Alzheimer’s disease, may also cause a smell disorder.

Scratch and sniff

Download this episodeSmell disorders are treated by an otolaryngologist, a doctor who specializes in diseases of the ear, nose, throat, head, and neck. An accurate assessment of a smell disorder will include, among other things, a physical examination of the patient’s ears, nose and throat, a review of their health history, such as exposure to toxic chemicals or injury, and a smell test. Some tests are designed to measure the smallest amount of odor that someone can detect. A scratch-and-sniff book may be used to quantify the level of loss. Diagnosis is important to identify and treat the underlying cause of a potential smell disorder. If the problem is caused by medications, the otolaryngologist may recommend lowering the dosage or changing the medicine to reduce its effect on the patient’s sense of smell. If nasal obstructions such as polyps are restricting the airflow in the nose, surgery may be needed to remove them and restore the patient’s sense of smell.

A sign of other conditions

Download this episodeYour sense of smell often serves as a warning signal, alerting you to spoiled food or a natural gas leak. When their smell is impaired, some people change their eating habits. Some may eat too little and lose weight while others may eat too much and gain weight. People who’ve lost their sense of smell sometimes try to boost flavor by adding more salt or sugar to their foods. But these additions might cause problems for those at risk for certain medical conditions, such as high blood pressure or diabetes. In severe cases, loss of smell can lead to depression. Problems with your chemical senses may be a sign of other serious health conditions. A smell disorder can be an early sign of Parkinson’s disease, Alzheimer’s disease, or multiple sclerosis. It can also be related to other medical conditions, such as obesity, diabetes, hypertension and malnutrition. Patients who suffer from a loss of smell should seek medical attention as soon as possible to determine the cause of their loss.Trusted by thousands of listeners every week, T. Glenn Pait, M.D., began offering expert advice as the host of UAMS’ “Here’s to Your Health” program in 1996. Dr. Pait began working at UAMS in 1994 and has been practicing medicine for over 20 years.