Are there things that others find to be normal but smell foul to you? Do you sometimes find it difficult to identify an odour? Do you sense an imaginary odour?
The probable reason behind this maybe a smell disorder!
How Smell Works
Your sense of smell comes from sensory cells (also called olfactory sensory neurons) which connect to the brain. These neurons are found in a small patch of tissue inside the nose and have odor receptors. Microscopic molecules released by substances around us stimulate these neurons. These molecules reach these neurons in two ways – either through your nostrils or through a channel that connects the roof of the throat to your nose. Once the neurons detect the molecules, they send messages to the brain to identify these molecules or smell.
Typically, we associate good odors with benefits (nutritious food, safe and pleasant experiences) and foul odors (stale food, smoke) with harm or risk. Some odors are subtle and act at a subliminal level without getting consciously registered e.g. perception of attraction, fear or illness.
Do You Have A Smell Disorder?
A smell disorder is the decreased ability to smell or a change in the way odor is perceived. The 4 types of smell disorders are:
- Hyposmia – This is reduced ability to detect odour. Nasal polyps usually obstruct nasal passageway leading to hyposmia. This happens due to sinus, trauma and upper respiratory disorders.
- Anosmia – This is the complete inability to detect odour. In some case, people are born with this condition which is also called congenital asomia. This may occur due to nasal congestions, aging, trauma or an effect of a medical condition like Alzheimers disease.
- Parosmia – Parosmia may be a change in the perception of the odour. For example, something that normally smells pleasant may now smell foul. When the olfactory sensory neurons are damaged due to conditions like upper respiratory tract infections, head injuries there may be a distortion in identifying the smell. Also, exposure to pesticides and chemicals may affect the olfactory sensory neurons which may result in sending wrong signals to the brain. This is why food might seem foul to you and fresh to another.
- Phantosmia – This may lead to a sensation of an odour that isn’t actually present. It is called olfactory hallucination. This may be a neurological problem where the nerve cells send abnormal signals to the brain.
How Serious Is A Smell Disorder?
It Affects Flavor
75% of what you perceive as taste comes from your sense of smell. Most of the time when people report the loss of the sense of taste, the real reason is a smell disorder!
When you eat something, the olfactory molecules in the foods are transmitted in the passage between your mouth and nose to the olfactory sensory neurons, which send messages to the brain. Simultaneously, the taste receptor cells located along the surface of the tongue help in detecting sweet, salty, sour, bitter and umami tastes and communicate the same to the brain. Information about taste and smell combine to provide a wholesome picture of flavor, which we generally perceive as the taste of food.
When there is a smell disorder, your ability to perceive the flavor of food is inhibited [1]. Now you know why your sense of taste is ruined when you have a cold.
It May Alter Eating Habits
When sense of smell is impaired, most people tend to change their eating habits; they either tend to eat too little or too much due to the alteration in taste. There is also the tendency to eat too much sugar or salt to improve the taste of food. This can cause diabetes, high blood pressure and kidney disease [2].
It May Affect Lifestyle
Patients with olfactory disorders are impaired in areas of food intake, safety, personal hygiene and in their sexual life. Many find cooking more difficult and have problems in detecting foul food. Sensing dangerous events such as a gas leak, smoke or fire becomes difficult. Personal hygiene, especially in the form of body odor or bad breath, might get affected, leading to hampered social relations including social communication, mate selection and reproductive function. For persons working as cooks or wine tasters, perfumers, nurses or firemen, olfactory disorders can be catastrophic, needing special adjustments or a job change [3].
It May Affect Brain Functioning
The olfactory bulb (the part of the brain that changes sensation into perception) is part of the limbic system, and the nose is closely related to this system and therefore triggers behavior, memory and mood. Olfactory disorder has been noted as an early warning sign for conditions like Parkinson’s disease, Alzheimer’s disease and Down syndrome [4].
Due to impaired quality of life and reduced enjoyment of food and environment, those with olfactory disorders may be more prone to loss of emotional control and depression. Depression can in turn cause reduced sexual drive, especially in men. According to studies, men with a reduced sense of smell exhibit a strongly reduced number of sexual relationships and women are affected such that they feel less secure about their partner [5].
References
- Taste and Smell, Society For Neuroscience
- Smell Disorders, National Institute of Deafness and Other Communication Diseases
- Olfactory Disorders and Quality of Life—An Updated Review, Oxford Journals
- Olfactory dysfunction in Parkinson disease, U.S National Library of Medicine
- Olfactory disorders and their consequences for quality of life, U.S National Library of Medicine
