Allergy, Nose & Sinus
Why can’t I smell or taste well during a cold or sinus infection?
February 10, 2020
Smell or olfaction, is one of the five human senses that is often overlooked. It plays an important role in the appreciation of food flavors and pleasant odorants (e.g. perfumes and flowers), detection of potential hazardous situations or materials (e.g. fire smoke and spoiled food) and is integral in a person’s daily social interactions and awareness of his or her surroundings. In this short blog, Dr Gan explains why we can’t smell when we have a cold and discuss some of the common causes of loss of smell and taste, an area that is often neglected not only by patients but also by some Family Physicians and Ear, Nose & Throat (ENT) Specialists.
Figure 1– The location of the olfactory nerves in the nose. When smell is detected by the olfactory nerves, the smell information is carried by signals that are transmitted by the olfactory bulb and olfactory tract to the brain.
Most of us has had a cold, flu or sinus infection (sinusitis) at some point in our lives (some more frequent than others). During these episodes, sometimes we would have experienced a temporary reduction or a total loss of our sense of smell and taste. The nerves responsible for detecting smell (also called the olfactory nerves) are located at the roof of the nasal cavity (deep and high inside the nose)(Figure 1). When one has a cold, flu or sinusitis, there is swelling and a lot more mucous in the nose. The mucous and swelling in the nose prevents the smell (odorant) from reaching the top of the nasal cavity. Hence the smell never reaches the smell nerves and the nerves are not stimulated. After your nose or sinus infection settles, the swelling and excessive mucous resolves. The odorant is then able to reach the smell nerve fibres again. Hence, you regain your sense of smell. Your sense of taste (ability to detect sweetness, sourness, bitterness and saltiness and umami) is actually normal during your cold or sinus infection. Your food seems “tasteless” during a cold because your appreciation of food flavour and odour comes from your ability to smell! So don’t blame your taste bud for the loss of flavour. It is all due to your stuffed-up nose!
Unfortunately for some, during the cold, flu or sinus infection, the loss of sense of smell is not due to a physical blockage. It is due to the virus, bacteria or inflammation causing damage to the smell nerves during the infection. If the smell nerves are damaged, the loss of smell is often permanent and irreversible. Most often, the cause for prolonged loss of sense of smell is unknown (Idiopathic). Other common causes of prolonged loss of sense of smell include severe head trauma (potentially causing shearing injury to the smell nerve), chronic sinusitis, nasal polyps and rhinitis. In rare instances the loss may be due to a nose or brain tumour!
If your sense of smell has decreased, you should consult a Singapore ENT Specialist for further assessment. A decrease in sense of smell (relative to what is considered normal for the patient’s age-group) is also increasingly recognised as an early marker for neurodegenerative conditions such as Parkinson’s disease and Alzheimer’s disease.
Dr Gan Eng Cern
ENT Specialist Singapore