An altered or bitter taste is a common symptom reported by people infected with COVID-19. This specific sensory change, known clinically as dysgeusia, is recognized as a distinct manifestation of the viral infection. This bitter or metallic taste can significantly affect appetite and quality of life. Unlike a simple stuffy nose that dulls flavor, this alteration suggests a direct interference with the body’s sensory pathways.
Understanding Dysgeusia and Taste Alterations
The senses of taste and smell are susceptible to disruption by the SARS-CoV-2 virus. A complete inability to smell is termed anosmia, while a total loss of taste is ageusia. Dysgeusia involves a distortion of taste perception, often manifesting as a bitter or metallic flavor.
This bitter sensation is a qualitative change, meaning the five basic tastes (sweet, sour, salty, bitter, umami) are not simply weaker, but are incorrectly perceived. The bitter taste can occur even when eating foods that should taste normal, or it may be a phantom taste present all the time. This taste distortion is often confused with parosmia, a distortion of smell that causes familiar odors to smell foul or repulsive. Since a large part of what we perceive as taste is actually derived from smell, damage to the olfactory system can also indirectly contribute to the overall distortion of flavor.
Biological Mechanisms Behind Taste Disruption
The virus gains entry into human cells by binding to the angiotensin-converting enzyme 2 (ACE2) receptor, present in cells within the nasal and oral cavities. In the olfactory system, the virus targets supporting cells (sustentacular cells), rather than directly attacking the olfactory sensory neurons. These sustentacular cells express the ACE2 receptor and provide metabolic and structural support to the smell-detecting neurons.
Infection of these support cells triggers an inflammatory response, damaging the cilia on the sensory neurons necessary for smell detection. This disruption in the supporting structure and the resulting inflammation temporarily compromises the signaling pathway from the nose to the brain. The misfiring or altered neural signals that result from this damage are thought to be incorrectly interpreted by the brain, contributing to both a loss of flavor and the distorted bitter perceptions.
A more direct mechanism occurs in the taste system, where the ACE2 receptor is expressed on Type II taste receptor cells within the taste buds. These Type II cells are responsible for detecting sweet, bitter, and umami tastes. Viral entry and replication in these taste cells can lead to their injury or death, directly interfering with the ability to perceive taste correctly. Stem cells responsible for regenerating new taste receptor cells can also be affected, disrupting the normal turnover process. This impairment in the renewal of taste cells may be a significant factor in the prolonged experience of altered tastes, including the persistent bitter sensation.
Typical Duration and Recovery Patterns
The duration of taste alteration following COVID-19 varies widely, though the symptom is often transient. For many people, the altered taste resolves relatively quickly, with the median time for taste loss recovery in mild cases being approximately eight days. Most people who experience this symptom during the acute phase of illness report improvement within four weeks.
For a smaller subset of patients, the altered taste can persist for an extended period, sometimes lasting months or longer. This protracted taste alteration is thought to be related to the slow regeneration of damaged cells. The stem cells that replace Type II taste receptor cells can take weeks to fully recover and restore the taste buds to their pre-infection state. Research suggests that approximately 90% of mildly symptomatic patients who experience this sensory loss eventually regain their senses within two years.
Strategies for Managing Altered Taste
Managing a persistent bitter taste involves a combination of sensory retraining and practical dietary adjustments to improve the enjoyment of food. Olfactory training (smell training) is frequently recommended, even for taste issues, because of the close link between the senses. This involves repeatedly sniffing a set of four different scents, such as rose, eucalyptus, lemon, and clove, twice daily to encourage neural pathway repair.
Dietary strategies can help override or mask the bitter perception, allowing for better nutritional intake. Focusing on foods with strong, distinct flavors and varying textures often makes eating more tolerable. Incorporating sharp or tart elements, like a squeeze of lemon or vinegar, can help balance the unpleasant taste. Similarly, marinating protein sources can mitigate the metallic or bitter notes that these foods often trigger.
Maintaining oral hygiene is important, as it can help reduce metallic taste linked to dry mouth or secondary oral issues. Brushing regularly and ensuring proper hydration are simple steps that can make a difference. If the altered taste is severe, persistent, or leads to significant weight loss, consult a healthcare professional for evaluation.