Relieve minor mouth and gum irritations with Colgate® Peroxyl Mouthwash. Peroxyl is a medicated mouthwash used to relieve minor mouth and gum irritations by killing germs and/or preventing them from spreading and causing infection. When Peroxyl® comes into contact with mouth tissue, oxygen is released in a bubbling action providing mechanical cleansing to flush out mouth debris and help in the relief of oral irritations.