The corner of the left eye is swollen and painful when you blink, which may be caused by mosquito bites, atopic dermatitis, granuloma and so on. 1. Mosquito bites: If mosquitoes bite the skin at the corner of the eye when you go out, it will easily lead to localized inflammation of the eye, the corner of the eye is swollen and painful when you blink, accompanied by itching symptoms. 2. Allergic dermatitis: If the corner of the eye is exposed to allergens, such as dust, pollen, mites, certain chemicals, etc., may lead to the skin around the corner of the eye to appear red, swollen, painful, itchy and other symptoms. 3. Granuloma: when the patient due to unhygienic use of the eyes and other conditions occur granuloma, will appear in the left corner of the eye is swollen a blink of an eye, accompanied by a foreign body sensation and other uncomfortable symptoms. When patients have a swollen corner of the left eye pain when blinking, should immediately go to the hospital, clear cause of the disease, and then follow the doctor’s instructions for treatment.