Loss of taste (dysgeusia) and smell (anosmia) were notable symptoms during the early stages of the COVID-19 pandemic. These sensory changes became a prominent indicator of SARS-CoV-2 infection. While other viral illnesses can cause similar effects, the widespread and distinct nature of taste and smell loss with COVID-19 drew significant attention. Understanding the current prevalence and underlying causes of these symptoms remains an ongoing area of study.
Taste and Smell Loss in Current COVID-19 Variants
The prevalence of taste and smell loss has shifted with the emergence of new COVID-19 variants. Early variants like Alpha and Delta caused these sensory changes in a significant portion of infected individuals, with rates as high as 50% for Alpha and 44% for Delta. However, with the widespread circulation of Omicron sub-variants, the likelihood of developing taste and smell loss has decreased considerably. One meta-analysis estimated the global prevalence of Omicron-induced olfactory dysfunction in adults at 3.7%, though this varied across populations; for instance, European ancestry populations reported around 11.7%, while others ranged from 1.9% to 4.9%. While less common, these symptoms can still occur with the latest variants.
How COVID-19 Affects Taste and Smell
The SARS-CoV-2 virus affects taste and smell through complex mechanisms, primarily involving specific cells in the nasal cavity. The virus does not typically infect the olfactory sensory neurons directly, which detect odors. Instead, it targets supporting cells known as sustentacular cells within the olfactory epithelium. These sustentacular cells express the ACE2 receptor and TMPRSS2 enzyme, which the virus uses to enter cells. Infection of these supporting cells leads to inflammation in the olfactory epithelium. This inflammation and damage can disrupt the function of olfactory sensory neurons and their cilia, crucial for odor detection. While the exact mechanism for taste loss is still being investigated, some research suggests the virus can also affect taste bud cells directly or through inflammation, leading to changes in taste perception.
Understanding Recovery from Altered Senses
Temporary Recovery
For many individuals, the loss of taste and smell due to COVID-19 is temporary, with senses returning within days or weeks. Studies indicate that a large percentage of those affected, approximately 88% to 90% of mildly symptomatic patients, regain their senses within two months to two years. The median recovery time for smell has been observed to be around 11.5 days, and for taste, approximately 10 days in some studies.
Persistent Alterations
However, a subset of individuals experiences persistent or long-term alterations, which can last for months or even over a year, becoming a component of Long COVID. These prolonged changes can include parosmia, where familiar odors are distorted and often perceived as unpleasant, and phantosmia, characterized by smelling phantom odors that are not actually present. These persistent conditions can significantly impact an individual’s quality of life, affecting appetite, nutrition, and overall well-being.
Coping with Persistent Taste and Smell Changes
Living with persistent taste and smell changes can be challenging, but several strategies can help manage these symptoms. Smell training, also known as olfactory training, is a widely recommended technique. This involves regularly smelling specific scents, such as rose, lemon, eucalyptus, and clove, for short periods multiple times a day to help retrain the olfactory nerves. This practice aims to stimulate the nerves and improve their ability to detect and differentiate odors. Adjusting dietary habits can also make eating more enjoyable. Focusing on the texture and temperature of food, rather than solely on flavor, can enhance the eating experience. Incorporating different textures and varying temperatures can make meals more appealing. Some individuals find that bland foods or those with strong spices can be more tolerable. Maintaining good oral hygiene and ensuring adequate nutrition are also important. If symptoms persist or significantly impact daily life, consulting a healthcare professional, such as an ENT specialist, is advisable for further guidance and support.