No discolouration at all occurs when using Bioniq Repair Tooth-Milk​​​​​​​. The product was specially developed for daily use and not as a special treatment. The mouthwash should be used after brushing or also in-between, e.g. after meals. Rinse your mouth with the mouthwash for around 20 seconds, do not swallow and do not rinse out with water.