The appearance of a hard bag under the left ear in the elderly may be related to sebaceous cyst, mumps, glandular lymphoma, etc. 1. Sebaceous cyst: Due to the obstruction of sebaceous gland excretion below the left ear, the excretions are increasing in the sebaceous gland cystic epithelium, which then swells to form a retention cyst and may form a hard bag. 2. Mumps: Mostly due to parotid virus infection, causing left parotid gland enlargement. The anatomical location of the parotid gland is just below the ear, and when inflammation occurs, a hard bag may also appear. 3. Adenolymphoma: Mostly seen in middle-aged and elderly men, it may be caused by age, gender, smoking, etc. The exact cause is unknown. It appears as a painless lump below the back of the ear that is round or oval to touch. When a hard lump appears under the left ear of the elderly, it is recommended to consult a doctor in time, follow the doctor’s instructions for further examination, clarify the cause with the help of the doctor, and carry out targeted treatment or therapy.