Saline nasal irrigation and gargling in COVID-19: a multidisciplinary review of effects on viral load, mucosal dynamics, and patient outcomes

Abstract

With unrelenting SARS-CoV-2 variants, additional COVID-19 mitigation strategies are needed. Oral and nasal saline irrigation (SI) is a traditional approach for respiratory infections/diseases. As a multidisciplinary network with expertise/experience with saline, we conducted a narrative review to examine mechanisms of action and clinical outcomes associated with nasal SI, gargling, spray, or nebulization in COVID-19. SI was found to reduce SARS-CoV-2 nasopharyngeal loads and hasten viral clearance. Other mechanisms may involve inhibition of viral replication, bioaerosol reduction, improved mucociliary clearance, modulation of ENaC, and neutrophil responses. Prophylaxis was documented adjunctive to personal protective equipment. COVID-19 patients experienced significant symptom relief, while overall data suggest lower hospitalization risk. We found no harm and hence recommend SI use, as safe, inexpensive, and easy-to-use hygiene measure, complementary to hand washing or mask-wearing. In view of mainly small studies, large well-controlled or surveillance studies can help to further validate the outcomes and to implement its use.

Keywords: COVID-19; gargling; nasal irrigation; nasal spray; nebulization; respiratory infection; saline.

Figure 1

Search strategy—clinical data.

Figure 2

Mechanisms of action of saline relevant to COVID-19. ACE2, angiotensin-converting enzyme 2; NET, neutrophil extracellular trap; ENaC, epithelial sodium channel; HOCl, hypochlorous acid formed through neutrophil myeloperoxidase activity in the presence of NaCl.

Figure 3

Clinical studies or reports of saline rinse or SI on SARS-CoV-2 viral load and clearance, stratified by method (gargling or nasal irrigation/spray) and the type of viral load (salivary, nasopharyngeal swabbed (NPS), or mid-turbinate): schematic overview of benefit–risk balance assessment. RTC, randomized clinical trial; non-RCT, non-randomized clinical trial; n, number of studies; CTls, controls; IS, isotonic saline (ISI, isotonic saline irrigation); HT, hypertonic saline; HClQ, hydroxychloroquine; PVI, polyvidone iodine; H₂O₂, hydrogen peroxide; ClHx, chlorhexidine; AUC, area under the curve of cumulative total symptom scores. Significant difference vs. controls or comparator: P < 0.05; non-significant P > 0.05.

Figure 4

Effect of saline rinse or nebulization in COVID-19 patients, stratified by disease severity and type of rinse/nebulization: schematic overview of benefit–risk balance assessment. See also Figure 3; comp, comparative; O2, oxygen; IS, isotonic saline; ISPLA, isotonic saline as placebo; HS, hypertonic saline; ARDS, acute respiratory distress syndrome; COPD, chronic obstructive pulmonary disease. Meaning of symbols: (A) respiratory symptoms (orange framed outcome) and (B) taste/smell disturbances (blue framed outcomes): “=”, effect comparable between treatment groups; “>”, generally better outcome with saline than with Ctls or comparator; “<”, comparator doing better than saline placebo; (C) risks: <, rate or severity outcome lower with saline than Ctls, comparator or reference population.