Loss of Smell After COVID: Anosmia, Hyposmia, and PRP Treatment

For many people, losing their sense of smell is one of the most recognizable effects of COVID-19. In some cases, smell returns relatively quickly. In others, the loss persists or the sense of smell changes in unexpected ways.

Persistent loss of smell after COVID can range from mild hyposmia to severe anosmia. Some patients develop parosmia, in which ordinary odors smell distorted or unpleasant. Others notice that food no longer has the same flavor.

When smell dysfunction continues, the key question becomes: What can be done about it?

Treatment begins with understanding the type and cause of the olfactory disorder. Depending on the diagnosis, management may include treatment of nasal or sinus disease, olfactory training, observation during recovery, or consideration of emerging treatments such as platelet-rich plasma, commonly called PRP.

Understanding COVID-Related Olfactory Dysfunction

Olfactory dysfunction is the medical term for an abnormality of the sense of smell.

It includes several conditions:

• Anosmia: complete or near-complete loss of smell
• Hyposmia: reduced ability to smell
• Parosmia: distorted perception of odors
• Phantosmia: perception of an odor that is not actually present

These disorders can have different causes and may require different treatments.

COVID-19 is one potential cause of persistent olfactory dysfunction, but it is not the only one. Viral infections, chronic rhinosinusitis, nasal polyps, allergies, head trauma, aging, certain medications, and neurological disorders can also affect smell.

That distinction is important when someone assumes that all persistent smell loss after COVID is automatically caused by the infection.

Anosmia: Complete Loss of Smell

Anosmia is the most severe form of smell loss.

Someone with anosmia may be unable to detect familiar odors such as coffee, perfume, citrus, soap, or cooking food. Because smell contributes substantially to flavor perception, anosmia can also make eating less enjoyable.

Anosmia can occur temporarily during an infection or persist afterward. Persistent anosmia warrants evaluation to determine whether the problem is related to post-viral olfactory dysfunction or another condition.

Hyposmia: When Smell Is Reduced but Not Gone

Hyposmia is a partial reduction in the sense of smell.

Patients with hyposmia sometimes describe the experience as “muted” smell. Strong odors may remain detectable while subtle aromas disappear. For example, someone may recognize that coffee is present but no longer appreciate the details of its aroma.

Because hyposmia can be gradual, some people do not realize how much their smell function has changed until they compare their ability to detect odors with how they smelled before. Formal smell testing can provide a more objective assessment.

Why Does COVID Affect Smell?

Smell depends on specialized sensory tissue located high within the nasal cavity and a complex pathway connecting the nose to the brain. COVID-19 can disrupt normal olfactory function through effects on the cells and tissues that support the olfactory system and through inflammatory processes.

Importantly, persistent smell loss does not necessarily mean that the nose is blocked. Some patients have substantial smell dysfunction despite having relatively little congestion. This is one reason that treatment aimed only at nasal congestion may not resolve post-COVID anosmia or hyposmia.

Loss of Smell and Loss of Taste Are Not Exactly the Same

Patients frequently describe their symptoms as “loss of taste and smell.” There is an important physiological distinction.

The tongue detects basic tastes, including sweet, salty, sour, bitter, and umami. Smell contributes heavily to flavor, particularly the complex aromas that distinguish one food from another. As a result, people with anosmia may still detect that something is salty or sweet but feel that the food itself has lost most of its flavor.

This is why an evaluation for a smell and taste disorder often needs to pay particular attention to olfactory function.

Parosmia: When Smells Come Back Wrong

One of the more unusual symptoms following COVID-19 is parosmia.

Instead of simply being unable to smell, a person may suddenly perceive familiar smells differently. Foods, coffee, cleaning products, perfumes, or other everyday odors may smell unpleasant or chemically altered. Parosmia can occur as the olfactory system changes during recovery.

Although the symptom can be disruptive, it should be evaluated in the context of the patient’s overall smell history rather than automatically interpreted as a sign that the condition is becoming permanent.

How Is Persistent COVID Smell Loss Evaluated?

The first step is determining exactly what has changed.

An evaluation may include:

Medical History

Your physician may ask when the smell loss began, whether it occurred during COVID-19, how severe it was, and whether there has been any improvement.

Other questions may address:

• Nasal congestion
• Allergies
• Chronic sinus symptoms
• Previous sinus surgery
• Head trauma
• Medication use
• Parosmia
• Phantosmia
• Changes in food flavor
• Previous viral infections

Nasal Examination

The nose and nasal passages can be examined for inflammation, polyps, structural abnormalities, infection, or other conditions that could interfere with smell.

Nasal Endoscopy

A nasal endoscope can provide a detailed view of areas that cannot be adequately examined with a routine nasal examination.

Smell Testing

Objective smell testing can help determine the degree of olfactory dysfunction.

Testing can also provide a baseline that may be useful when evaluating response to treatment.

Imaging When Appropriate

CT or MRI may be recommended in selected patients depending on the symptoms, medical history, examination findings, and suspected cause.

The goal is to avoid treating the wrong problem.

Treatment Options for Loss of Smell After COVID

Treatment should be individualized.

There is no single medication or procedure that restores smell for every person with post-COVID anosmia or hyposmia.

Potential treatment strategies include:

1. Treating Underlying Nasal and Sinus Conditions

If chronic rhinosinusitis, nasal polyps, allergy-related inflammation, or another nasal problem contributes to the loss of smell, treatment may focus on that condition.

A sinus-related cause should be distinguished from post-viral olfactory dysfunction because the management may be very different.

2. Olfactory Training

Olfactory training is a structured form of smell rehabilitation.

It involves repeatedly smelling selected odors over time in an effort to stimulate and retrain the olfactory system.

Recent randomized-trial evidence and meta-analyses support olfactory training as a useful non-invasive approach for COVID-related olfactory dysfunction, although studies have used different protocols and additional research is needed to determine the optimal program.

Olfactory training may be particularly useful because it does not require a procedure and can be incorporated into a longer-term rehabilitation strategy.

3. PRP Treatment for Persistent Smell Loss

For selected patients with persistent olfactory dysfunction, platelet-rich plasma (PRP) is an emerging treatment option.

PRP is prepared from the patient’s own blood. Platelets are concentrated and then used as part of a targeted treatment intended to support tissue healing and regeneration.

The concept is particularly relevant to nerve-related olfactory dysfunction because the olfactory system has regenerative capacity.

However, PRP should be approached as an evolving treatment rather than a guaranteed solution.

What Does the Research Say About PRP for Anosmia?

Research on PRP for olfactory dysfunction has expanded considerably since the COVID-19 pandemic.

A 2025 systematic review and meta-analysis examined randomized controlled trials involving PRP for COVID-related olfactory dysfunction. The analysis included four randomized trials with 198 participants and found statistically significant improvements in objective and subjective smell scores, as well as a higher response rate among patients receiving PRP. The researchers also reported that PRP was generally well tolerated in the included trials.

Earlier systematic-review evidence also reported improvement in olfactory scores following topical PRP for persistent post-COVID smell impairment.

At the same time, the evidence has limitations.

The number of randomized studies remains relatively small, treatment protocols differ, and researchers continue to study which patients are most likely to benefit.

The practical takeaway is that PRP is promising, but it is not appropriate to describe PRP as a guaranteed cure for anosmia or hyposmia.

Who May Be a Candidate for PRP?

PRP is not automatically appropriate for everyone with smell loss.

Before considering treatment, a physician should determine:

• Whether the patient actually has measurable olfactory dysfunction
• Whether the loss is complete or partial
• Whether the symptoms are likely post-viral
• Whether there is an underlying nasal or sinus condition
• Whether there is a history of head trauma
• Whether another medical condition could explain the symptoms
• Whether the potential benefits of treatment justify the procedure

A detailed evaluation is particularly important because different causes of anosmia can require very different treatments.

What Happens During PRP Treatment for Smell Loss?

At the NY Otolaryngology Group, the PRP protocol begins with an evaluation that may include a questionnaire, nasal and sinus examination, nasal endoscopy, and smell testing. Imaging such as CT or MRI may be recommended when appropriate.

If the patient is considered an appropriate candidate, the nose is anesthetized before the PRP is administered near the olfactory fibers.

The current practice protocol calls for two treatments approximately one month apart, followed by a three-month follow-up evaluation. The practice also recommends structured smell therapy following PRP treatment.

The exact treatment plan should be determined by the treating physician based on the patient’s diagnosis and clinical circumstances.

PRP for Hyposmia vs. PRP for Anosmia

Both anosmia and hyposmia are forms of olfactory dysfunction, but the degree of impairment is different.

A person with anosmia has little or no functional smell perception.

A person with hyposmia retains some smell ability but at a reduced level.

Because PRP research has generally examined olfactory function rather than simply assigning patients to a single diagnosis, treatment candidacy should be based on the complete clinical picture rather than the label alone.

Objective smell testing can be particularly helpful when determining the severity of dysfunction and monitoring changes over time.

Can PRP Improve Taste?

The relationship between smell and taste can make this question complicated.

PRP research for COVID-related dysfunction has primarily evaluated olfactory outcomes.

If reduced flavor perception is caused largely by impaired smell, improvement in olfactory function may allow a patient to experience food and beverages more normally again.

However, PRP should not be presented as a proven treatment for every type of primary taste disorder.

A patient whose symptoms are truly related to the taste system rather than the olfactory system may require a different evaluation.

PRP and Smell Training: Can They Be Combined?

Olfactory training and PRP address the problem from different angles and may be incorporated into the same treatment strategy in appropriate patients.

Olfactory training provides repeated sensory stimulation. PRP is a procedural treatment being investigated for its potential regenerative effects on the olfactory system.

The combination is an area of clinical interest, but patients should not assume that combining treatments automatically produces better results. Treatment should be individualized based on the available evidence and the patient’s condition.

The practice’s current PRP approach includes smell therapy following treatment.

How Long Does Post-COVID Smell Loss Last?

Recovery varies.

Some patients recover quickly, while others have persistent anosmia, hyposmia, or altered smell perception.

A prolonged course does not necessarily mean that improvement is impossible. Recent research continues to investigate rehabilitation and procedural treatments for patients whose symptoms persist.

At the same time, persistent smell loss should not automatically be attributed to COVID simply because it began after an infection.

A complete evaluation can help identify other potentially treatable causes.

Why Persistent Anosmia Should Not Be Ignored

Smell contributes to quality of life, appetite, food enjoyment, and the perception of flavor.

It also provides an important safety function.

People with significant anosmia may not detect smoke, gas leaks, spoiled food, or other environmental odors.

If your smell is substantially reduced, functioning smoke and carbon-monoxide detectors and appropriate food-safety precautions become especially important.

When Should You See a Smell and Sinus Specialist?

Consider an evaluation if:

• Your smell has not returned after COVID-19.
• You can detect only strong odors.
• Food continues to taste unusually bland.
• Smells have become distorted.
• You experience phantom smells.
• Your symptoms are persistent or worsening.
• You have chronic congestion or sinus symptoms.
• You have a history of head trauma.
• The condition is affecting your appetite or quality of life.
• You want to know whether you may be a candidate for PRP.

The goal is not simply to label the condition as “post-COVID smell loss.”

The goal is to determine what type of olfactory dysfunction you have, what may be causing it, and which treatments are appropriate.

Find Out What Is Causing Your Loss of Smell

Persistent loss of smell after COVID, whether it presents as anosmia, hyposmia, or parosmia, deserves a careful evaluation.

At the New York Sinus Center, evaluation of smell disorders can help distinguish post-viral olfactory dysfunction from nasal and sinus conditions and other causes of impaired smell.

For appropriate patients, treatment options may include olfactory training and discussion of emerging therapies such as PRP treatment for loss of smell.

If you have been living with persistent smell loss, schedule an evaluation to determine what may be contributing to your symptoms and which treatment options may be appropriate for you.