Allergic reaction: This is the most likely diagnosis due to the sudden onset and localized nature of the edema. Allergic reactions to insect bites, pollen, or other environmental allergens can cause rapid swelling of the eyelid.

Insect bite or sting: Similar to an allergic reaction, an insect bite or sting can cause localized edema and swelling of the eyelid.
Contact dermatitis: Irritation from contact with certain substances like makeup, soap, or chemicals can lead to eyelid edema.
Blepharitis: Inflammation of the eyelid margin can cause swelling and edema, although it typically affects both eyelids.
Hordeolum (stye): A localized infection of the eyelid margin can cause swelling and edema, often accompanied by pain and redness.

Orbital cellulitis: A serious infection of the tissues surrounding the eye, which can cause eyelid edema, proptosis, and vision changes. If left untreated, it can lead to severe complications, including vision loss and intracranial infection.
Angioedema: A potentially life-threatening condition characterized by rapid swelling of the eyelids, face, and airways, often associated with an allergic reaction or genetic disorder.
Cavernous sinus thrombosis: A rare but deadly condition caused by a blood clot in the cavernous sinus, which can lead to eyelid edema, proptosis, and cranial nerve deficits.

Wegener's granulomatosis: A rare autoimmune disorder that can cause inflammation and swelling of the eyelids, as well as other systemic symptoms.
Sarcoidosis: A condition characterized by granulomatous inflammation that can affect the eyelids, lungs, and other organs.
Eyelid lymphedema: A rare condition caused by abnormal lymphatic drainage, which can lead to chronic eyelid swelling.
Tumor or cyst: A rare possibility, where a benign or malignant tumor or cyst can cause localized swelling of the eyelid.