Lower eyelid swelling can be caused by allergy, mosquito bites, eye inflammation, blepharospasmal cysts and heart and kidney diseases. 1. Allergy: the use of poor quality cosmetics, or contact with environmental dust, pollen, etc., can cause an allergic reaction, localized redness, swelling, itching symptoms, the appearance of swelling of the lower eyelid. 2. Mosquito bites: after being bitten by mosquitoes at the lower eyelid, redness, swelling, pain and other symptoms may appear locally, which may be manifested as swelling of the lower eyelid. 3. Ocular inflammation: when blepharitis and other ocular inflammation occurs, the stimulation of inflammation can cause redness and swelling of the lower eyelid, and localized pressure and pain symptoms. 4. Blepharoplasty: Blepharoplasty openings are blocked, local secretions gather and stimulate the surrounding tissues, which can lead to chronic granulomatous inflammation, and localized cystic changes can occur, manifesting as swelling of the lower eyelids. 5. Cardiac and renal diseases: cardiac insufficiency, nephritis and other cardiac and renal diseases can also lead to fluid retention in the lower eyelid, causing lower eyelid swelling. 6. Other: drinking too much water, sleeping in an improper position resulting in poor facial blood circulation and other factors can also cause water retention, resulting in symptoms of lower eyelid swelling. If the swelling of the lower eyelid cannot be relieved by rest for a long time or is accompanied by other discomforts of the body, you should consult a doctor in a timely manner, and actively carry out the treatment under the guidance of specialists, which will help to alleviate the discomforts as soon as possible.