24th September 2020, Dr Chee L Khoo
Since Covid-19 pandemic started 6-7 months ago, there have been a deluge of reports coming out in the medical and lay press and sometimes it is hard to keep track of what is real and what is just logical. Because Covid-19 is primarily a respiratory pathogen, infection begins in the nasal and nasopharyngeal mucosa with high viral load especially at the beginning of the infection. It is logical to believe that nasal irrigations may play a role in reducing viral load and hence, viral transmission and viral severity. Is it just logical (like many other things you read on google) or is there a medical basis to the suggestion? Further, what about topical corticosteroids? Do they do the opposite and increase viral transmission and viral severity?
Scientific basis of saline wash
The nasal mucosa has an important role in against inhaled viruses, bacteria, and other particulates. The mucosa lining has a superficial mucus layer sitting on an aqueous base. It traps inhaled particulates that are then propelled by underlying cilia into the nasopharynx. They are ultimately ingested into the gastrointestinal system, where they are destroyed.
Theoretically, nasal saline (isotonic or hypertonic) rinses physically disrupt the viscous surface layer, removing the mucus and its associated particulate matter. Nasal saline helps to increase hydration of the deeper aqueous layer, simultaneously improving the underlying ciliary beat frequency and reducing local inflammatory mediators.
When the nasal mucosa is inflamed when infected or due to allergens, the muco-cillary function is disturbed. Saline wash of the nasal passage, mouth, and throat would probably eliminate or reduce viral load in the body mechanically at least in the initial stage of the pathogenesis. hypertonic saline gargles and nasal wash may work in preventing the disease and may also be useful in reducing nasopharyngeal viral load to provide symptomatic relief. Further, it may reduce viral shedding and reduce the transmission of the illness. This may break the chain of infection.
It has been theorised that hypertonic saline (HS), which has higher osmolarity, pulls water out of cells resulting in increased hydration of the aqueous portion of the mucus layer. This improves muco-ciliary clearance while also decreasing epithelial oedema. The possible mechanism of action of HS gargles and nasal wash is the chlorite ion; which the cells in nasal and pharyngeal mucosa convert to hypochlorous acid, which has anti-viral properties (1). The presence of hypertonic saline can result in calcium efflux from epithelial cells, stimulating ciliary function and improving muco-ciliary clearance.
Does it help? – the evidence
There is ample evidence which confirms the benefits of isotonic saline nasal wash in improve peak expiratory flow rate, quality of life. For example, Wang et al (2) found nasal saline wash benefited children with acute sinusitis in symptoms. In a random control trial Ramalingam et al (1) noted that after the onset of viral illness, volunteers who were practicing hypertonic nasal saline irrigation and gargles had 36% lesser use of over-the-counter medications (P = 0.004), 35% lesser transmission (P = 0.006), and viral shedding (P = 0.04). A recent randomized clinical trial evaluating the utility of HS for mitigation of the common cold demonstrated HS reduced duration of illness, over-the-counter
medication use, transmission to household members, and viral shedding (3).
However, Cochrane meta-analysis emphasized the need of random control studies with larger number of subjects to substantiate beneficial effects of nasal wash (4).
Does nasal irrigation do harm?
Well, it’s all great and logical that we can wash away the contaminants on the nasal mucosa including viral or bacterial particles. Do irrigations of the nasal cavities increase viral shedding, and thus transmission? Further, is there concern about viral contamination of the nasal rinse bottle itself, leading to increased transmission through contact-induced infections?
There is evidence with rhinovirus that the virus is detectable in nasal lavage, suggesting that viral contamination of surfaces may occur via rinsing (4,5). This surface contamination is important to recognise because evidence has suggested that if the virus is Covid-19, then the virus may be stable on plastic and can be detected more than 72 hours after exposure (6). This is critical to communicate for patients who already use these therapies for rhinosinusitis management.
Importantly, the lavage fluid, rinse bottle, and surrounding surfaces may become contaminated and serve as a source of infection in the future. Thus, patients should practice good hand hygiene and decontaminate the surrounding surfaces (eg, sink, counters) and plastic rinse bottle to prevent subsequent infection.
Does it help if we add something in the nasal wash?
A Cochrane systematic review of 3 double-blind, randomised clinical trials of intranasal steroids (fluticasone or beclomethasone) for management of upper respiratory tract infections found no evidence that intranasal steroid sprays improved symptom severity or duration (4). However, the review did not find any harm from intranasal steroids.
Betadine and other iodine derivatives have also been proposed to reduce viral load in the nasal cavity. In a recent review by Parhar et al the role in povidone iodine, a common surgical preparation, was evaluated (7). While they did not find many clinical trials, there was significant evidence of povidone-iodine resulting in substantial coronavirus reduction in in vitro studies. They
identified 3 different studies of prior coronavirus epidemics in which topical application of povidone-iodine resulted in significant viral titre reduction. Furthermore, a prospective trial of 0.08% diluted povidone iodine rinses in 29 patients demonstrated safety and tolerance by patients (8).
For our patients with chronic rhinosinusitis, continued use of steroid irrigations should be encouraged. We await more research to shed further light on saline irrigation’s protective and therapeutic effect on COVID-19. The other main entrance to the body for the COVID-19 is the mouth. It is known that an oral rinse with antimicrobial agents is efficacious in reducing the viral load in oral fluids.
- Ramalingam S, Cai B, Wong J, Twomey M, Chen R, Fu RM, et al. Antiviral innate immune response in non-myeloid cells is augmented by chloride ions via an increase in intracellular hypochlorous acid levels. Sci Rep. 2018;8:13630.
- Wang YH, Yang CP, Ku MS, Sun HL, Lue KH. Efficacy of nasal irrigation in the treatment of acute sinusitis in children. Int J Pediatr Otorhinolaryngol. 2009;73:1696–701.
- Ramalingam S, Graham C, Dove J, Morrice L, Sheikh A. A pilot, open labelled, randomised controlled trial of hypertonic saline nasal irrigation and gargling for the common cold. Sci Rep. 2019; 9(1):1015. doi:10.1038/s41598-018-37703-3
- Hayward G, Thompson MJ, Perera R, Del Mar CB, Glasziou PP, Heneghan CJ. Corticosteroids for the common cold. Cochrane Database Syst Rev. 2015;(10):CD008116.
- Lee SB, Yi JS, Lee BJ, et al. Human rhinovirus serotypes in the nasal washes and mucosa of patients with chronic rhinosinusitis. Int Forum Allergy Rhinol. 2015;5(3):197-203. doi:10.1002/alr.21472
- Jin Y, Yang H, JiW, et al. Virology, epidemiology, pathogenesis, and control of COVID-19. Viruses. 2020;12(4):E372. doi:10.3390/v12040372
- Parhar HS, Tasche K, Brody RM, et al. Topical preparations to reduce SARS-CoV-2 aerosolization in head and neck mucosal surgery. Head Neck. 2020;42(6):1268-1272. doi:10.1002/hed.26200
- Panchmatia R, Payandeh J, Al-Salman R, et al. The efficacy of diluted topical povidone-iodine rinses in the management of recalcitrant chronic rhinosinusitis: a prospective cohort study. Eur Arch Otorhinolaryngol. 2019;276(12):