Blepharitis: This is an inflammation of the eyelids that can cause redness, swelling, and irritation. It's a common condition and often presents with these symptoms, making it a likely first consideration.

Conjunctivitis (Pink Eye): This condition, often viral or bacterial, causes the conjunctiva to become inflamed, leading to redness and swelling of the eyelid. It's highly contagious and common, especially in children.
Hordeolum (Stye): A localized infection or inflammation of the eyelid margin involving hair follicles of the eyelashes or meibomian glands. It presents as a painful, red, swollen nodule on the eyelid.
Chalazion: A small bump on the eyelid due to a blocked oil gland. While often painless, it can become inflamed and cause swelling and redness of the eyelid.

Orbital Cellulitis: A serious infection of the tissues surrounding the eye, which can lead to severe complications if not promptly treated. Symptoms include redness, swelling, and pain around the eye, with possible decreased eye movement.
Angioedema: A condition characterized by rapid swelling of the dermis, subcutaneous tissue, mucosa, and submucosal tissues. It can cause significant swelling of the eyelids and, if part of an allergic reaction, can be life-threatening.
Herpes Zoster (Shingles): When it affects the eye, it's known as herpes zoster ophthalmicus. It can cause a painful rash on the eyelid and around the eye, leading to redness and swelling.

Malignant Tumors: Such as basal cell carcinoma or squamous cell carcinoma, which can present as a non-healing ulcer or nodule on the eyelid, potentially causing swelling and redness.
Wegener's Granulomatosis (Granulomatosis with Polyangiitis): A rare autoimmune disorder that can affect various parts of the body, including the eyes, leading to inflammation and damage.
Sarcoidosis: A condition that can cause inflammation in various parts of the body, including the eyes. Ocular manifestations can include uveitis, conjunctivitis, and eyelid swelling.