Ask about the use of Enzyme Mouthwash (eq Propolinse, 1:4 Concentrate).
Is the % used in the formula necessary to be 20% as recommended?
Are there any substances that are forbidden to be added to the formula? will not cause brown stains after gargle?
Or do you have any advice on how to use it? Try putting it in a general mouthwash formula and it won't cause brown stains after spitting.