There's a hard pack behind the back of the ear.

There is a hard bag behind the back of the ear, which is considered to be due to the large distribution of sebaceous glands behind the back of the ear. However, the patient's recent unreasonable diet and unreasonable living habits cause endocrine disorder, resulting in excessive sebum secretion from sebaceous glands and gland duct blockage. Meanwhile, this symptom may also induce infection, thus causing pain and other symptoms.