Allergic Conjunctivitis: This is a common condition in adolescents, often triggered by environmental allergens such as pollen, dust, or pet dander. Symptoms include bilateral eye swelling, redness, itching, and tearing, which align well with the presentation of bilateral eye swelling.

Blepharitis: An inflammation of the eyelids that can cause swelling, redness, and itching. It's common in adolescents and can be associated with poor eyelid hygiene or conditions like acne.
Conjunctivitis (Viral or Bacterial): While often unilateral, conjunctivitis can present bilaterally, especially if the cause is viral. Symptoms include redness, discharge, and swelling of the conjunctiva.
Contact Dermatitis: An allergic reaction or irritation from substances like makeup, contact lens solution, or certain chemicals, leading to eyelid swelling and redness.

Orbital Cellulitis: A serious infection of the tissues surrounding the eye, which can cause swelling, redness, and pain. It requires prompt antibiotic treatment to prevent serious complications.
Thyroid Ophthalmopathy: Associated with Graves' disease, this condition can cause bilateral eyelid swelling, proptosis, and eye movement abnormalities. It's crucial to identify due to its systemic implications.
Kawasaki Disease: Although more common in younger children, Kawasaki disease can present with bilateral conjunctival injection (without exudate), among other symptoms like fever, rash, and lymphadenopathy.

Wegener's Granulomatosis (Granulomatosis with Polyangiitis): A rare autoimmune disorder that can affect various parts of the body, including the eyes, causing inflammation and swelling.
Sarcoidosis: A condition characterized by the growth of granulomas (inflammatory cells) in various parts of the body, including the eyes, which can lead to uveitis and eyelid swelling.
Angioedema: A rare condition that can cause rapid swelling of the skin and mucous membranes, including the eyelids, often associated with an allergic reaction or genetic predisposition.