A small bump on the upper eyelid can be caused by granuloma, chalazion, mosquito bites and so on. 1. Blepharitis: usually due to staphylococcal infection, and also associated with poor hygiene in the eyelid area, unclean hands in contact with the eyes and other factors. Blepharitis is usually characterized by a hard nodule, which can be accompanied by redness, swelling, pain and other symptoms, and looks like a small bump on the upper eyelid. 2. Chalazion: It is usually caused by a blockage of the secretion outlet of the blepharoplasty glands, resulting in retention of secretions. Patients often appear in the eyelid lumps, most of the no special symptoms, which can also be manifested as a small bump on the upper eyelid. With the development of the disease, there can be blocked vision, foreign body sensation, blurred vision and so on. 3. Mosquito bites: Mosquito bites on the eyelids can also occur, manifested as small bumps on the upper eyelid. It is recommended that patients who have a small bump on the upper eyelid, accompanied by obvious discomfort, consult a doctor for a clear diagnosis, and follow the doctor’s instructions to actively treat.