Here at Cheeki we use the best quality materials that have no added chemicals. As a result, your silicone shield may develop dark spots resembling mould. This happens to any water bottle however, because our silicone is blue it makes it easier to see. To prevent this from happening we recommend regular cleaning with our CHANGE Water Bottle cleaning tablets and allowing for the bottle to completely dry out.  Please note the mould you see is most likely clean it just leaves an unpleasant stain!