More about teeth whitening: Once you have started a teeth whitening treatment, do not take things that can discolor your teeth, for example. red soda or red wine. Do not do this because 48 hours after starting treatment, the bleach draws water out of your teeth and therefore they will absorb dyes faster. After another 48 hours, everything will normalize and you can eat normally again. You need to know that your teeth and gums can be more sensitive and irritated after a teeth whitening. This is completely normal and will go away in a few days.