One upper eyelid is swollen without pain or itching.

Swelling of the upper eyelid on one side—without pain, itching, or other symptoms—is a relatively common clinical presentation that can arise from several underlying causes. While often benign and self-limiting, it warrants careful evaluation to rule out more serious conditions. Common non-inflammatory causes include localized fluid retention (e.g., due to sleep position, mild allergic exposure, or transient sodium retention), subtle trauma (such as unnoticed rubbing or minor impact), or early-stage chalazion—particularly if a small, firm, non-tender nodule is palpable near the eyelid margin. Less commonly, unilateral eyelid edema may reflect systemic issues such as thyroid eye disease (though this typically involves bilateral involvement and other ocular signs like proptosis or lid retraction), renal or cardiac dysfunction with asymmetric fluid distribution, or, rarely, orbital or adnexal pathology including neoplasms or lymphoproliferative disorders. Importantly, absence of pain and pruritus makes acute bacterial infection (e.g., preseptal cellulitis) or typical allergic reactions less likely—but does not entirely exclude them, especially in atypical or early presentations. A thorough history—including onset, duration, associated visual changes, systemic symptoms (e.g., fatigue, weight change, hypertension), medication use, and prior similar episodes—is essential. Physical examination should assess eyelid contour, symmetry, skin texture, presence of induration or fluctuance, conjunctival appearance, extraocular motility, visual acuity, and pupillary responses. If swelling persists beyond 7–10 days, worsens, or is accompanied by vision changes, diplopia, proptosis, or systemic symptoms, prompt referral to an ophthalmologist or appropriate specialist is recommended for further evaluation, which may include imaging (e.g., orbital ultrasound or MRI) or laboratory testing.