The loss of smell and taste following a cold or other upper respiratory viral infection is medically known as post-infectious olfactory dysfunction (PIOFD). This common issue can make food bland and removes an important layer of safety from daily life. While many individuals recover spontaneously, this process can be slow and unpredictable, sometimes taking weeks or months. Fortunately, specific, evidence-based methods can actively encourage the nervous system to regain function and accelerate recovery.
Why Colds Affect Smell and Taste
The loss of smell, which often presents as a loss of taste, occurs because the viral infection directly impacts delicate structures high inside the nasal cavity. The common cold causes significant inflammation and swelling of the nasal passages, physically preventing odor molecules from reaching the receptors in the olfactory cleft. This temporary physical blockage is often the initial cause of smell loss, usually resolving quickly once congestion clears.
In more persistent cases, the virus causes direct damage to the olfactory epithelium, the specialized tissue responsible for detecting odors. Viruses often target and destroy the supporting cells, disrupting the environment necessary for the neurons to function. This intense inflammation and cell destruction can lead to the temporary loss of nerve endings.
The perceived loss of “taste” is mostly a loss of flavor perception, since approximately 80% of a food’s flavor profile relies on the sense of smell. The tongue registers only five basic tastes: sweet, sour, salty, bitter, and umami. When the sense of smell is compromised, the complex nuances of flavor are lost, making even favorite foods seem muted and unappetizing.
Olfactory Retraining: The Key Recovery Method
The most widely recommended non-pharmacological strategy for recovering from PIOFD is olfactory retraining, often referred to as smell training. This process functions like physical therapy for the nose and brain, using repetition to stimulate the regrowth of olfactory nerve pathways. It capitalizes on the neuroplasticity of the brain and the regenerative capacity of the olfactory neurons.
The standard training involves consistently sniffing four distinct scent categories to stimulate different sets of smell receptors. The four categories typically used are:
- Flowery (like rose)
- Fruity (like lemon)
- Resinous or camphor-like (like eucalyptus)
- Spicy or aromatic (like clove)
It is recommended to use essential oils for strong, consistent scent delivery, but natural sources like spices can also be used.
The procedure requires focused attention, performed twice daily for a minimum of three to six months. For each scent, a person should inhale gently for about 15 to 20 seconds while concentrating on the memory of what the object should smell like. This mental association is thought to be as important as the physical stimulation in encouraging the brain to reconnect sensory input with correct perception. After three months, it is beneficial to switch to a second set of four scents to provide novel stimulation to regenerating nerve cells.
Reviewing Medical Treatments and Supplements
Beyond behavioral training, several medical and supplemental interventions have been investigated to help recover the sense of smell. Corticosteroids, powerful anti-inflammatory agents, are sometimes prescribed to reduce swelling in the nasal passages. Nasal steroid sprays may deliver medication directly to the olfactory region, though their effectiveness for prolonged PIOFD varies based on the timing and extent of nerve damage.
Oral corticosteroids, such as a short course of prednisone, are occasionally used in the early stages of smell loss to aggressively reduce inflammation. However, evidence supporting the use of systemic steroids for PIOFD is limited, and they carry potential side effects requiring careful discussion with a healthcare provider. Olfactory training remains the only intervention with consistent scientific support as a first-line treatment.
Many popular supplements, including Zinc, Alpha-Lipoic Acid, and Vitamin A, are frequently discussed but lack conclusive scientific evidence for treating PIOFD. Vitamin A is thought to support the healing of the olfactory neuroepithelium, but studies are often small. The benefits of Vitamin A are most pronounced when used as an intranasal application in combination with smell training. Overall, the data supporting the use of supplements to reverse post-viral smell loss is weak or inconclusive.
Recovery Timelines and When to See a Specialist
Recovery from post-viral smell loss is highly variable and requires patience, as it depends on the body’s ability to repair damaged tissues. For many experiencing PIOFD following a common cold, the sense of smell returns relatively quickly, often within a few days or weeks, especially if the cause was primarily congestion. When the olfactory epithelium has been damaged, however, the recovery timeline can extend to several months.
The issue is considered prolonged or chronic if the sense of smell has not returned or shown improvement after three to six months. This extended recovery period is normal in cases of nerve-related damage, since the regeneration of olfactory sensory neurons is a slow biological process. Improvement is often gradual, manifesting first as a distortion of smells, known as parosmia, before full function is restored.
If no improvement is noted after six to eight weeks of loss, or if the loss is unilateral (in only one nostril), a consultation with a specialist is recommended. An Otolaryngologist, also known as an ENT doctor, can perform an examination to rule out other causes of smell loss, such as nasal polyps or chronic sinusitis. A specialist can confirm the PIOFD diagnosis and provide personalized guidance on maximizing recovery through structured olfactory training and medical options.