The doctor was right about that, but this doesn't mean the product is dangerous. Hydrogen and oxygen combine to form water, but if you collect hydrogen you can make a dangerous bomb out of it, or if you so choose run a car with it.
Both products (colosan and oxypowder) basically share the same formula. Ozon (O3)is very reactive and must be handled with care. When combined with magnesium and released into the body, though, it is totally harmless and it right away breaks down into oxygen, thereby helping the body remove waste and revitalize cells.
Colosan is not so much an expeller of waste as you can expext in laxatives as it is breaking down waste into minute particles. It is therefore less likely for it to produce jungs of old crusts. It liquifies waste by combing with hydrogen, forming waterery stools.