One of the most common long-term symptoms resulting from Covid-19 infection is loss of taste or smell. A recent case series investigated laser therapy for this problem. Subjects rated their degree of loss of taste on a scale of 0-10 with 10 being the worst with complete loss. The typical pre-treatment scores were between 6 and 10 which is severe to complete loss.
Treatment involved a series of laser treatments to the tongue with low level or “cold” laser. These are pulsed lasers which do not produce the intense heat as do surgical lasers. The simple treatments which take approximately 10 minutes involve treating multiple areas of the tongue and is completely painless. Following the laser protocol, the taste scores were between 2 and 0 which is slight loss or complete resolution.
This result is not surprising. Low level laser is well supported by research in resolving neuropathy which often involves the arms/hands and legs/feet in severe disorders. Taste is mediated by nerve endings in the tongue which are commonly referred to as “taste buds”. Different taste sensations are perceived in different areas of the tongue so the treatment works across the whole surface of the tongue. They can be injured by viral infections. Covid-19 seems to do this more aggressively than many other infections.
The same group of researchers performed a similar study on those with loss of sense of smell related to post-Covid-19 syndrome. They used a 0 to 10 smell analog scale to rate the degree of impairment. Subjects’ scores before laser therapy were between 7 and 10, or severely impaired to no sense of smell. Following therapy, the scores were typically between 0 and 2, or mild to no impairment.
The similar improvement in smell perception with low level laser is surprising given that that sensation is also the result of activation of nerve endings in the nasal passages.Loss of smell may have a more significant implication as the nerve that transmits that to the olfactory or smell center in the brain is more direct. Loss of smell has been linked to cognitive loss in the early phases of diseases such as Alzheimer’s.
The old saying, “time heals all wounds” is more accurately, time heals some wounds but laser will take care of the others. Typically those with long-Covid-19 symptoms have persisted over a longer interval suggesting they need a little more help such as low level laser therapy.
Campos et al. A Brazilian multicenter pilot case series on the efficacy of photobiomodulation therapy for COVID-19-related taste dysfunction. Photodiagnosis and Photodynamic Therapy, 23 Nov 2021.
Soares et al. Intranasal photobiomodulation therapy for COVID-19-related olfactory dysfunction: A Brazilian multicenter case series. Photodiagnosis and Photodynamic Therapy 36 (2021) 102574.