There are several factors that can cause teeth to become discoloured, including ageing, consumption of certain foods and drinks (such as coffee, tea, and red wine), smoking, and poor oral hygiene. While these are the most common factors, there are many lesser-known causes of tooth discolouration. For example, certain medications may cause the teeth to become darker in colour. Antihistamines, antipsychotics, and high blood pressure medications may all lead to tooth discolouration due to chemicals that become deposited within the enamel of the teeth over time. Beyond these medications, cancer treatments such as radiation therapy may also contribute to changes in tooth colouration.