Signs of orbital cellulitis are acute pain on opening the mouth, eyelid swelling, unilateral prolapse of the nictitating membrane, forward displacement of the globe, and conjunctivitis. Keratitis may develop from lagophthalmos. The condition is seen predominantly in large and hunting breeds of dogs and is rare in other species. Foreign bodies (eg, migrating grass awns) and zygomatic sialadenitis are additional causes. Orbital hemorrhage and neoplasia may mimic inflammation, except there is usually no pain on opening the mouth. In acute cases, systemic broad-spectrum antibiotics are usually curative, but if swelling behind the last molar is present, drainage of this area is indicated. Warm compresses and topical lubricants to protect the cornea are also indicated. Relapses may occur, and radiographs and ultrasonography of the adjacent teeth, sinuses, and nasal cavity are recommended.