Eyelids are red, swollen and itchy, most commonly due to eyelid skin allergies, mosquito bites and wheals. 1. Eyelid skin allergy: when the eyelids come into contact with external allergens, such as irritating skin care products, pollen, animal hair, dust mites, the skin of the eyelids will be allergic to the phenomenon, which is mainly manifested as redness, swelling, itching and other discomforts of the eyelids. 2. Mosquito bites: In daily life, mosquito bites on the eyelid skin can easily lead to redness, swelling and itching, and most of the bites can be observed on the skin surface. 3. Eyelid swelling: Eyelid swelling, that is, blepharitis, when the glands of the eyelids are infected by bacterial suppurative infection, in the early stage of the onset of the disease, some patients may appear red, swollen, itchy and other discomforts. The redness, swelling and itchiness of the eyelids are not relieved for a long time, and it is recommended that the patient go to the hospital for examination in a timely manner, to clarify the specific causes, and to carry out targeted treatment.