Usually not wash your hair when you are full and not take a bath when you are hungry, mainly because washing your hair after you are full may cause poor blood supply, which in turn may cause ischemia and fainting. And if you take a bath when you are hungry, especially a hot bath or sauna, it may cause vasodilatation of the whole body, reduce the blood flow throughout the body, resulting in ischemia and thus cause discomfort, including poor blood supply to the heart or head, and then cause a series of diseases, and in severe cases, may directly fainting. Need to pay attention and concern, but do not get entangled in the details.