The 3 drops of 3% is totally false. Every copy of the cleanse I have seen is X number drops of 35% food grade H2O2 (Hydrogen-Peroxid) in at least 8 oz of pure water.
As for H2O2 (Hydrogen-Peroxid) in the blood, water is absorbed into the blood almost instantaneously if needed from the stomach and first part of the small intestine. If that water just happens to contain nascent oxygen from H2O2, it also is absorbed really quick into the blood. Water doesn't stay in the stomach near as long as food does.