Compared to many members of the animal kingdom, human beings rank pretty low in smelling ability. A dog’s sense of smell is a million times as keen as ours. Among individual humans, the variation in smelling ability is enormous.
Researchers have found that people have different sensitivities to a particular odor. Some can detect a lower level than others. Eating asparagus, for example, gives urine a strong, distinctive odor, but only 10 percent of the public can pick up this odor in low concentrations. The vast majority of people do not detect it at all. According to researchers, every person has an odor blind spot. There is evidence that at least some of the individual differences in smell ability are hereditary.
Women can smell better than men. The ability to smell diminishes with age. Smokers do not smell as well as non-smokers. Two out of every three people have temporarily lost their sense of smell because of a cold, allergy, accident, or some other cause. The people who have lost their sense of smell completely suffer from a problem that doctors call anosmia. People who have reduced ability to detect odors, far below normal levels, suffer from hyposmia.
Some people have peculiar smell disorders. They smell things “the wrong way”- For instance, the ones who think skunk odors are great. People with that kind of problem do not usually complain, but doctors see a lot of patients with the opposite defect: They are bothered by persistent unpleasant odors that no one else seems able to detect. They find normally pleasant odors, like that of a rose, unbearably obnoxious.
Smell disorders are also common during pregnancy. Sometimes during pregnancy, a woman finds that her ability to smell goes haywire. Things that used to smell good don’t anymore. Doctors are not sure why this happens. Some think it may be due to the extra hormones in the mother-to-be blood.
Diseases may cause smell disorders. Epilepsy can do strange things to a person’s sense of smell. For a few days before a seizure, some epileptics find that familiar things don’t smell the way they usually do. In some cases of epilepsy, a strong odor abruptly ends a seizure. Scientists are still speculating about why these things happen.
Head injuries have resulted in temporary or even permanent loss of smell for thousands of people. An infection in the upper respiratory track may temporarily block the nasal passages and interfere with smell. Allergies also block the nasal passages and can produce temporary smell disorders.
Polyps or growths in the nasal or sinus activities can lead to hyposmia or even anosmia. Hormonal problems have led to smell problems in some cases.
Illnesses such as Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, and others often result in hyposmia or anosmia. In rare cases, the cause of smell disorders is a brain tumor. Even cavities in the teeth can result in difficult with smelling.
The mental illness Schizophrenia is often accompanied by many strange smell effects. Sometimes medical treatments for an ailment can result in a loss of smell sensitivity.
A loss of smell also means a great reduction of the ability to taste foods. People suffering from anosmia or hyposmia often lose their appetite and their enjoyment of food. They tend to neglect good eating habits and may end up suffering from malnutrition. Many people who suffer from smell disorders become depressed. They lose their capacity to enjoy many of life’s pleasures.
Anosmia can have many different causes. Some people are born with the disorder. The cause may be a hereditary lack of some important enzyme. But most people develop anosmia because of an accident or illness, or due to the aging process. It is estimated that more than half of all people over sixty-five years have serious smell disorders, with many suffering from a total loss of smell.
Finding out if a person has a smell disorder is not easy as diagnosing many other ailments. In fact, researchers and their colleagues often disagree on whether a particular patient really has a smell problem at all.
