for people ages 18 years and up (full criteria)
at San Francisco, California
study started
estimated completion
Principal Investigator
by Stuart Gansky
Headshot of Stuart Gansky
Stuart Gansky



In this pilot trial, 150 confirmed COVID-19 individuals will be randomly assigned to 1 of 5 groups: distilled water, CloSYS Ultra Sensitive Rinse (Rowpar Pharmaceutical Inc., USA), Oral-B Mouth Sore (Oral-B, USA), Crest Pro-Health Multi-Protection (Crest, USA), or Listerine Zero (Johnson and Johnson, USA). Study participants will be asked to rinse/gargle with 10-20ml (according to the rinse instructions) of the assigned solutions 4 times per day, for 30-60 seconds, for 4 weeks.

Official Title

Effect of Antiseptic Mouthwash/Gargling Solutions and Pre-procedural Rinse on SARS-CoV-2 Load (COVID-19)


SARS-CoV-2, the virus causing COVID-19, has affected vulnerable individuals, especially those with comorbidities, and high exposure health care workers (HCWs). Typically, the virus first colonizes in the upper respiratory tract (URT) causing clinical symptoms such as coughing, sore throat, and then is transferred to the lower respiratory tract (LRT) which can lead to severe pneumonia, acute respiratory distress syndrome (ARDS), sepsis, and death, if it is not managed. The World Health Organization (WHO) has presented comprehensive guidelines underscoring personal hygiene measures including respiratory hygiene against SARS, MERS, influenza, and now SARS-CoV-2 / COVID-19. While personal protection equipment (PPE), personal hygiene measures, environmental infection control, and physical distancing are crucial in mitigating disease transmission, respiratory hygiene measures do not prevent SARS-CoV-2 colonization in URTs and LRTs of infected individuals (symptomatic and asymptomatic). Experimental and clinical research studies on infections similar to COVID-19 such as SARS, MERS, and H5N1 have shown that using antiseptic mouthwash/gargling solutions, such as products containing chlorhexidine gluconate (CHG), polyvinylpyrrolidone iodine (PVP-I), chlorine dioxide (ClO2), cetylpyridinium chloride (CPC), and hydrogen peroxide (H2O2) can reduce viral load. A randomized controlled trial (N=387) showed efficacy and cost-effectiveness of gargling with water or a product containing PVP-I (3X/day, 20 seconds) on URTIs in healthy volunteers (18-65 years) over 60 days from a societal perspective; in vitro studies have shown that CloSYS, an over the counter mouthwash containing ClO2, was effective on inactivating SARS-CoV as well as disinfecting dental unit waterlines, and biofilm control in ultrasonic dental scaling units. A recent study has shown that CloSYS Ultra Sensitive Oral Rinse reduced the viral load of SARS CoV 2, SARS CoV, and Influenza A H3N2 to a varying extent. The data show that the viral load reduction of SARS CoV 2 by Ultra Sensitive rinse was 10 fold more than the reduction of SARS CoV in 30s. Recently, the US Centers for Disease Control (CDC) and the American Dental Association (ADA) have recommended using a mouthwash containing 1.0-1.5% H2O2 as a pre-procedural rinse before dental treatment to potentially reduce SARS-CoV-2 load; however, no in vivo clinical studies have been conducted to support this claim. The aim of this pilot trial is to evaluate the effect of four over-the-counter antiseptic mouthwash/gargling solutions compared to a control (distilled water) to reduce SARS-CoV-2 load. In addition, study participants will be assessed for the severity of their clinical symptoms during the study period. The 4-week protocol was selected as studies have shown that patients can continue to shed the virus and potentially transmit it to the others for a 2 to 4 week period. An interim analysis is planned when 10 participants per arm (50 total) complete the study using the alpha-spending function with O'Brien-Fleming boundary rule.


COVID-19 SARS-CoV 2 Severe Acute Respiratory Syndrome Coronavirus 2 Virus Disease Coronavirus Infections Pharyngeal Diseases Anti-Infective Agents, Local Mouthwashes Gargle Saliva Severe Acute Respiratory Syndrome Virus Diseases Hydrogen Peroxide Listerine Cetylpyridinium Chlorine dioxide Oral-B Mouth Sore mouthwash Crest Pro-Health Multi-Protection mouthwash CloSYS Ultra Sensitive Rinse mouthwash Distilled water Listerine Zero Mouthwash Product Oral-B Mouth Sore (H2O2) mouthwash Crest Pro-Health Multi-Protection (C21H38ClN) mouthwash CloSYS (ClO2) mouthwash Listerine Mouthwash


You can join if…

Open to people ages 18 years and up

  • Tested positive for COVID-19 with a sample collected in the prior 7 days
  • Ability to read and speak English or Spanish
  • Ability to participate in the study for 4 weeks
  • Being asymptomatic or having mild or moderate symptoms (for example, sore throat, coughing, fever, fatigue)
  • Ability to rinse/gargle
  • Not having any condition that might worsen with gargling solutions
  • Not having a history of mouthwash sensitivity
  • Not having an allergy to any mouthwash that has been used before
  • Not using another mouthwash/gargling solution since the most recent positive test
  • Not taking antimicrobial medications (antibacterial, antiviral, antibiotics including off-label FDA-approved medications such as hydroxychloroquine)
  • Anticipated ability to participate in the study for 4 weeks
  • Have a cellphone and agree to receive text messages for reminders to use mouthwash during the day and for follow-up visits, and can videoconference (like zoom) on a cellphone, tablet, or computer for sample collection instructions

You CAN'T join if...

  • People who because of their symptoms intend to receive antiviral medications that could potentially affect viral load in their saliva samples
  • Pregnant or lactating women due to potential aversions to mouthwash solution taste/smell.


  • University Of California, San Francisco accepting new patients
    San Francisco California 94143 United States

Lead Scientist at UCSF

  • Stuart Gansky
    I am Professor, Associate Dean for Research, and Lee Hysan Chair of Oral Epidemiology in the School of Dentistry and Director of the UCSF Center to Address Disparities in Children's Oral Health (CAN-DO) and a Co-Director of the Research Coordinating Center to Reduce Disparities in Multiple Chronic Diseases.


accepting new patients
Start Date
Completion Date
University of California, San Francisco
Trial website Eligibility Assessment
Phase 2 research study
Study Type
Expecting 150 study participants
Last Updated