Research has found that tea stains contain toxic substances such as cadmium, lead, mercury, arsenic, and carcinogens like nitrites. These substances adhere to the smooth surface of tea cups and enter the digestive system when drinking tea. They combine with proteins, fatty acids, vitamins, and other nutrients in food, forming insoluble sediments that not only hinder the body's absorption and digestion of nutrients but also damage organs such as the stomach and intestines.

In addition, teacups that are not cleaned regularly can accumulate significant scale, which also contains heavy metals that are harmful to health.

The thicker the tea stains, the harder they are to clean. Therefore, daily cleaning and regular maintenance should not be overlooked. Experts recommend that after each tea session, even if there are no visible stains on the tea set, it should be thoroughly cleaned to prevent buildup over time.

If tea stains have accumulated and are difficult to remove, they can be soaked overnight with heated rice vinegar or baking soda, then scrubbed with a toothbrush for easy cleaning. Alternatively, placing citrus juice or other fruit juices in the cup for a few hours can also help remove tea stains.