Your teeth are like sponges... they absorb.

Your teeth have pores just like your skin or a sponge. Anything you put in your mouth that has color will absorb into those pores. Wine, coffee, dark berries, and smoking are extremely active in staining teeth. Over time, the natural color of your teeth becomes darker due to these stains. These stains will never go away unless you actively remove them. Properly formulated teeth whitening gel works by absorbing into your teeth and gently pushing stains out through the pores.