Loss of smell and taste caused by the COVID-19 and the role of traditional Chinese medicine

Zuobiao (Roy) Yuan, Lic. Ac, PhD

Disclaimer: Although I am a licensed acupuncturist in the state of Minnesota, this article is purely an introduction to the public. If the reader is diagnosed with COVID-19 or has any suspected symptoms, please go to the local hospitals first. Any treatment plan discussed in this article cannot replace professional medical advice, diagnosis or treatment, and readers should not rely solely on the information provided in this article to meet their own medical needs. Chinese herbs are currently not approved by the FDA and are not a medicine in the United States, but it can be used for health consultation. Reading this article does not mean that there is a physician-patient relationship. If readers want to try Chinese herbs, please consult a local experienced professional acupuncturist or herbalist.

According to current data, as many as 80% of people who tested positive for the SARS-CoV-2 have a subjective dysfunctional sense of smell or taste. In the COVID-19, loss of smell is very common, because the receptor of SARS-CoV-2 is abundantly expressed in the cells of the human nasal cavity and olfactory tissue. Loss of taste is usually interacted with loss of smell. Interestingly, loss of smell and taste usually means that the condition will not progress to severe illness.

The prognosis of this loss of smell and taste varies in different reports. A report from South Korea suggests that more than 90% of patients will eventually recover within five weeks of the onset of the disease; but another report from Italy shows that by the fourth week of the onset, the recovery rate is just over 60%. Maybe this is related to the specificity of race.

The main mechanism leading to the loss of smell and taste is that this virus causes inflammation in the nose, which may cause the loss of smell or olfactory neurons, especially for people with long-term or permanent loss of olfactory function. Further research found that the loss of olfactory nerves mainly occurred in olfactory epithelial cells, rather than olfactory neurons. The following figure is a schematic diagram of olfactory epithelium and olfactory neurons (olfactory bulb). Olfactory epithelial cells are located in the nasal cavity, while the olfactory bulb is located in the skull.

Perhaps this is why after the dysfunctional smell and taste occurs, unlike general nerve damage, its recovery is relatively fast.

When the olfactory dysfunction (OD) caused by the SARS-CoV-2 can improve by itself, there is no need to take specific treatment measures. However, if the injury persists for more than 2 weeks, treatment should be considered. Current recommended treatments include olfactory training, as well as intranasal sodium citrate, intranasal vitamin A, and systemic omega-3. However, to date, there is no evidence that these therapies are effective.

There have been some reports on the Internet about using acupuncture and Chinese medicine to help the loss of smell and taste caused by the SARS-CoV-2. But I haven't seen any papers published in academic journals. The published papers mainly focus on abnormal smell post virus infection. Although they are not aimed at the SARS-CoV-2, these experiences are still useful.

Common acupuncture points for acupuncture are: Du 16 (Feng Fu), DU 20 (Bai Hui), LI20 (Ying Xiang), LU 7 (Lie Que), LU 9 (Tai Yuan), ST36 (Zu San Lli), and SI3 (Hou Xi). The main mechanism of choosing these points is for local stimulation, stimulation of the brain center, and stimulation of lung meridian, since the sense of smell belongs to the lungs in Chinese medicine theory. There are two papers suggesting that acupuncture can promote the recovery of the loss of smell after virus infection (1,2)。

In terms of traditional Chinese medicine (TCM), the existing Internet reports include: Shengmai Decoction, Buzhong Yiqi Decoction, Ganlu Xiaodu Dan, Shashen Maidong Decoction, Chai Ge Decoction, etc. It is mainly based on the symptoms of the patients, such as dry mouth and nose, fatigue, unclear residual heat, etc., respectively, and differentiate these symptoms into different TCM patterns, such as deficiency of both qi and yin, spleen deficiency, dampness and heat, lung and stomach yin deficiency, wind-cold invasion, etc., and then give the corresponding Chinese herbs.

Kampo medicine in Japan is originated from Chinese medicine. One of the prescriptions, Tokishakuyakusan (TSS, Danggui Shaoyao San), contains some blood-activating and dampness-draining drugs such as Angelica, Chuanxiong, Alisma, Poria, etc. In clinical trials, if the drug is used with conventional treatments, the effective rate of olfactory dysfunction post virus infection can be increased from 29% to 60%, which is more than doubled. Even patients who do not respond to conventional treatment have a 43% improvement rate (3). The product has also been confirmed in animal experiments, for the mechanisms of promoting repair and proliferation of olfactory epithelium, which is significantly better than the control group, as shown in the figure below. It can also promote the growth of nerve growth factor (NGF) (4). The product has been cited in the Clinical practice guidelines for the management of olfactory dysfunction by the Japanese Rhinologic Society, so it is worthy of attention.

In my personal experience, it is necessary to give individualized prescriptions based on the patient's TCM patterns, and add some herbs of moving blood and opening the orifices. At the same time, you must be patient and complete the entire course of treatment. Generally one month is a course of treatment, and the evaluation is made every three months. Then the prognosis is usually good. It should be noted that the shorter the symptoms occur, the better the prognosis. For example, the prognosis of four weeks after the onset is better than six months after the onset, so early management is needed.

I also gave an English lecture for this topic and uploaded it to YouTube. Although English is not authentic, if someone in need sees it, it may be helpful to them.

This is the link：https://www.youtube.com/watch?v=5oLxr6lt12M&t=22s.

Literatures：

1. Vent J, et al. Effects of traditional Chinese acupuncture in post-viral olfactory dysfunction. Otolaryngol Head Neck Surg. 2010 Apr;142(4):505-9.

2. Dai Q et al. Recovery of olfactory function in post viral olfactory dysfunction patients after acupuncture treatment. Evid Based Complement Alternat Med. 2016;2016:4986034.

3. Miwa T, et al. Clinical practice guidelines for the management of olfactorydysfunction — Secondary publication. Auris Nasus Larynx. 2019 Oct;46(5):653-662.

4. Noda T et al. Effects of Tokishakuyakusan on Regeneration of Murine Olfactory Neurons In Vivo and In Vitro. Chem Senses. 2019 May 29;44(5):327-338.