COVID-19 Associated Loss of Smell and Wound Care

Loss of smell, or anosmia, is a common presenting symptom in COVID-19 with reported incidence rates of 33-74%^1,2. Many patients who present with anosmia have little to no respiratory symptoms³. Patients with anosmia tend to be younger and have a milder COVID-19 disease course⁴. In the sub-acute recovery period following COVID-19, loss of smell and taste is the most prevalent long-lasting symptom⁵. Anosmia can be a debilitating symptom associated with depression⁶, and its association with loss of taste can lead to malnutrition. Your sense of smell can appreciate various aromas, alerts you to danger, and helps you define your environment. Those suffering from sub-acute and chronic anosmia are seeking medical care looking for answers to when they can expect their sense of smell to return and if there is anything they can do to speed up the process. Wound specialists are among those seeking answers as we use our sense of smell routinely when assessing patients and their wounds. Wound specialists use their sense of smell to identify potential wound odors that may indicate infection, but clinicians can also identify incontinence, self-care deficits, GI bleeds, urinary tract infections, bacterial vaginosis, and C. difficile infection from the odor within an exam room.

Wound odor can be a useful assessment component during the clinical exam. Odor can be due to dressing saturation and necrotic tissue, so this component of the wound assessment is typically re-evaluated after cleansing, topical antiseptic use (such as hypochlorous acid), and debridement of necrotic tissue. Many wounds will have a slight odor, but a strong odor, especially one that persists after a thorough cleansing regimen, suggests heavy bioburden or infection⁷. Anaerobic bacteria like clostridium and bacteroides are major producers of wound odor, but some aerobic bacteria are also associated with causing wound odor, such as proteus, klebsiella, pseudomonas, and MRSA^8-10. Some volatile metabolites and fatty acids that cause wound odors have been described as cadaverine and putrescine and can be so intensely acrid that they induce vomiting¹¹. Evaluating odor is a subjective assessment, one that varies based on the capacity of the examiner but one that can add information to the wound exam. Experienced wound professionals who are exposed to a variety of wound odors may even be able to discern pathogens by the odor, such as the mousey odor of Pasteurella, a common contaminate from household pets like dogs¹².

Why does COVID-19 makes you lose your sense of smell? We know that with SARS-COV-2, the primary cellular entry receptor is the angiotensin-converting enzyme 2 (ACE2) receptor^13,14. ACE2 is expressed in various tissues, including the epithelial cells in the airway, endothelial cells lining the vascular system, and in a variety of organs, including the brain, heart, kidneys, and lungs^13,15-16. A natural place to investigate the source of COVID-19 anosmia would be the nerves in the nasal passages involved in the sense of smell. Still, investigators found little evidence of viral involvement that would contribute to anosmia¹⁷. However, the tentacular cells named due to their tentacle-like appearance as they wrap and support the scent-associated nerves in the upper airway did express ACE2 and were susceptible to viral involvement^17,18. The association between COVID-19 anosmia and younger patients and those with a milder disease course may be due to differences in immune response in tentacular cells. In patients with mild COVID-19, the local immune response is stronger and produces lots of IgA, limiting the virus's ability to spread and cause more severe disease. This local inflammatory reaction in tentacular cells, which we know express ACE2, could be why younger patients and patients with milder disease courses have a higher association with anosmia⁴. COVID-19 anosmia is also likely due to the generalized inflammation and mucous production associated with other upper respiratory viral infections known to cause both temporary and, less commonly, permanent anosmia.

Wound clinicians who have lost their sense of smell due to COVID-19 have inquired as to expected recovery. Most patients regain their sense of smell within a week or two. One study found that of patients with olfactory dysfunction, so both partial and total loss of smell related to COVID-19 infection, 15.3% hadn’t recovered function at 60 days, and only 4.7% hadn’t recovered function at six months². They also found patients were more likely to have protracted olfactory dysfunction recovery if they initially presented with complete loss of smell. Scent retraining can be a helpful method of restoring smell. A typical scent retraining regimen includes smelling essential oils one at a time while focusing on how you remember the scent. This is performed a few times a day until the sense of smell is recovered.

Wound odor is one facet of a complete patient and wound assessment. Until the sense of the smell is recovered, wound providers can ask patients or other clinicians if they detect an odor or rely on the other signs and symptoms of infection, imaging devices that measure bacterial load, laboratory findings, and wound cultures to guide their treatment recommendations.

References

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