Sniff, sniff. Imagine the smell of a stargazer lily or of fresh baked bread. Imagine throwing open the window on one of spring’s first warm days and smelling the sweet air. These are some of life’s free gifts.

But also imagine if smell was missing. None of us really notice all the smells around us, but for those whose sense of smell is diminished or missing, it can be a significant loss.

Olfaction is the sense of smell. It’s part of a person’s chemical sensing system, along with the sense of taste. Normal smell occurs when odors around a person, like the fragrance of flowers or the smell of baking bread, stimulate specialized sensory cells, called olfactory sensory cells which are located in a small patch of tissue high inside the nose.

Odors reach the olfactory sensory cells via two pathways. The first pathway is by inhaling, or sniffing, through the nose. When people think about smell, they generally think of this pathway.

The second pathway is less familiar. It is a channel that connects the roof of the throat region to the nose. When chewing food, aromas are released that access olfactory sensory cells through this channel. Congestion due to a head cold or sinus infection can block this channel, which temporarily affects the ability to enjoy the flavors of food.

But what are odors? They are small molecules that are easily evaporated and released into the environment and that stimulate these sensory cells. Once the olfactory sensory cells detect the odor molecules, they send signals to the brain, where the person can identify the smell and its source.

For most people, a problem with smell is a minor irritation, but for others it may be a sign of a more serious disease or long-term health condition. According to the National Institute of Health, problems with smell become more common as people get older.

Consider:

• 24.5 percent (15 million) of Americans 55 years old or older have a smell problem.
• 30 percent of older Americans between the ages of 70 and 80 have a problem with the sense of smell.
• Two out of three people over 80 have a problem with their sense of smell.
• A person’s sense of smell generally declines when he or she is over 60.
• Only one to two percent of people under the age of 65 will experience some problem with their sense of smell.
• Women of all ages are generally better at detecting odors than men.

There are five types of smell loss:

• Presbyosmia – Smell that declines with age. It is not preventable.
• Hyposmia – The ability to detect certain odors is reduced. This smell disorder is common in people who have upper respiratory infections or nasal congestion. This is usually temporary and goes away when the infection clears up.
• Anosmia – This is when someone can’t detect odor at all. This type of smell disorder is sometimes the result of head trauma in the nose region, usually from an automobile accident or chronic nasal or sinus infections.
• Dysosmia – This is a change in the perception of odors. Familiar odors may become distorted, or an odor that usually smells pleasant instead smells foul. Sometimes people with this type of smell disorder also experience headaches, dizziness, shortness of breath, or anxiety.
• Phantosmia – This is when someone perceives a smell that isn’t present at all.

If someone thinks they have a smell disorder, it’s time to visit the doctor. Diagnosis is important because once the cause is found, the doctor may be able to treat it. Many types of smell problems are reversible, but if they are not, counseling and self-help techniques may help the person cope.