- Just one patch fully treats most canker sores - Immediate Pain Relief - Protects the sore - stops pain from food, drink and irritants - Sticks to any canker sore and becomes a clear gel patch - Stays on comfortably for 8 to 12 hours, then dissolves - Won't come off while eating - Freshens breath - Contents treat 4-6 canker sores Canker Cover is a tablet-like patch made from edible ingredients. It sticks to any canker sore within seconds, and then forms a clear, gel patch that lasts 8 - 12 hours. The patch protects the sore from irritants - food, drink, braces, etc., a single patch will treat most canker sores.