The sudden swelling of the lower left eyelid may be caused by trauma, atopic dermatitis, blepharitis, etc. Patients should consult a doctor in time to clarify the cause of the disease and then treat it. 1. Trauma: If the patient has had a collision or fall before the sudden swelling of the lower left eyelid, then it should be considered trauma, and the patient can be relieved by applying cold compresses, etc. The patient can also be relieved by applying cold compresses. 2. Allergic dermatitis: if the patient is in contact with dust, pollen after the left lower eyelid suddenly swollen piece, should be considered to be allergic dermatitis, such patients should avoid re-exposure to allergens, if necessary, comply with the doctor’s orders to use loratadine and other drugs for treatment. 3. blepharitis: Staphylococcus aureus and other infections caused by blepharitis can also cause sudden swelling of the lower left eyelid, the patient will also have local redness, pain, can use erythromycin ophthalmic ointment, etc. for treatment. The left lower eyelid suddenly swollen piece, after rest for a long time can not be relieved, it is recommended that timely medical treatment. All of the above drugs should be used under the guidance of a doctor, do not self-medication.