The swollen red eyelid is a common presentation in primary care. An understanding of the anatomy of the orbital region can guide care. Factors that guide diagnosis and urgency of care include acute vs. subacute onset of symptoms, presence or absence of pain, identifiable mass within the eyelid vs. diffuse lid swelling, and identification of vision change or ophthalmoplegia. Superficial skin processes presenting with swollen red eyelid include vesicles of herpes zoster ophthalmicus; erythematous irritation of contact dermatitis; raised, dry plaques of atopic dermatitis; and skin changes of malignancies, such as basal or squamous cell carcinoma. A well-defined mass at the lid margin is often a hordeolum or stye. A mass within the midportion of the lid is commonly a chalazion. Preseptal and orbital cellulitis are important to identify, treat, and differentiate from each other. Orbital cellulitis is more often marked by changes in ability of extraocular movements and vision as opposed to preseptal cellulitis where these characteristics are classically normal. Less commonly, autoimmune processes of the orbit or ocular tumors with mass effect can create an initial impression of a swollen eyelid.