Lots of different factors can cause teeth yellowing and discoloration. The foods you eat and drink, certain medications, and age might all be contributing factors. Beverages like red wine, coffee, and tea can leave surface stains on the enamel of your teeth and turn your teeth yellow. Big contributors include tobacco and smoking, too.
Eventually, these surface stains can become even harder to remove because they go beneath the enamel to the dentin of your tooth.