Common causes
Swelling around the eyes can come from many mechanisms. Frequent causes include allergic reactions (allergic conjunctivitis or contact dermatitis), eyelid inflammation (blepharitis), eyelid infections like stye (hordeolum), blocked oil glands (chalazion), periorbital or orbital cellulitis, and sinus infections. Non-infectious factors such as trauma, fluid retention from high salt intake, sleep changes, and systemic conditions (kidney or heart-related fluid retention, thyroid disorders) can also cause or worsen swelling.