There are a number of factors that can cause the staining or discoloration of your teeth. Among the reasons are as follows: Smoking – Tobacco use can create stains on the teeth that are difficult to remove. There are two ingredients in tobacco that are the culprits of darker teeth: tar and nicotine. Tar is naturally dark while nicotine is colorless but turns yellowish when mixed with oxygen. Food & Beverages– Certain dark colored food and beverages such as coffee, tea, and red wine cause teeth stains. Their intense color pigments called chromogens stick to your teeth enamel causing discoloration. Aging– As you grow old, your enamel, which is the white outer shell of your teeth wears off. As a result, the softer and more yellowish part of your teeth called the dentin becomes more apparent. Medications – Teeth staining can be a side effect of certain medications such as antihistamines, antipsychotics, and certain high-blood pressure drugs. Even babies exposed to some antibiotics when their teeth are forming may have discoloration in their teeth later in their adult life. Trauma – Accidents that impact the mouth may affect your teeth color. Your tooth reacts to an injury by laying down more dentin, which is the darker layer of your teeth under the enamel.