Preseptal cellulitis is infection and inflammation anterior to the orbital septum and confined to periorbital soft tissues and eyelids. The globe and orbital structures posterior to the septum are not infected; thus, pupillary reaction, visual acuity, and ocular motility should not be affected. Sinusitis is the most common cause of preseptal cellulitis; other causes include local skin abrasions, hordeolum, or insect bites. Common pathogens are S pneumoniae, S aureus, S pyogenes, and H influenzae (nonimmunized children). Patients present with eyelid swelling, erythema, tense edema, warmth, and tenderness. Tense edema may cause eye closure and the patient may be unable to open the eye spontaneously. Low-grade fever is often present. Differential diagnosis includes orbital cellulitis, allergic conjunctivitis, contact dermatitis, chalazion/hordeolum, necrotizing fasciitis, viral conjunctivitis with secondary eyelid swelling, idiopathic orbital inflammation, thyroid ophthalmopathy, dacryoadenitis, dacryocystitis, rhabdomyosarcoma, and trauma.