Answer: Tea is harmful to humans in four cases, which are as follows:

 1) If it is consumed too much: it causes stomach and duodenal ulcers

 2) If it was boiled so much that it turned dark brown: it causes disturbances in the heart muscle, constipation and laziness in the digestive system

 3) If it is drunk immediately after eating: it causes indigestion, so it is preferable to drink it an hour after eating.

 4) If it is drunk on an empty stomach, it means on an empty stomach or during hunger: where a layer called (chitinous) forms on the inner membrane of the stomach and intestine, which prevents the exit of digestive juices and causes constipation and indigestion.

 It causes patients with kidney stones and patients with stomach ulcers or duodenal ulcers.