spread of infection including visual disturbances, altered mental status, and sepsis Clinical Assessment The primary concern when making the diagnosis of periorbital cellulitis is to rule out the possibility of orbital cellulitis The cardinal signs of orbital cellulitis include decreased or painful eye movement, proptosis, changes in vision (e.g., change in acuity, decreased color vision, or visual field deficits), and papilledema (or other signs of optic nerve involvement such as Marcus Gunn pupil) Patients with orbital cellulitis may be irritable, toxic, and have a fever, but the presence of fever and leukocytosis are not sensitive enough markers to discriminate between the two conditions Due to the presence of the orbital septum which acts as a structural barrier, the eyelid swelling of orbital cellulitis typically does not extend beyond the superior orbital rim onto the brow The ED clinician should be aware that acute periorbital edema and erythema can also occur without infection Insect bites and allergic reactions can cause dramatic acute periorbital swelling, typically with minimal induration or tenderness, and oftentimes with pruritus These conditions are not usually associated with fever Often, close inspection of the skin with magnification can localize a site of an insect bite Swelling related to systemic allergic reactions is often bilateral, whereas periorbital cellulitis is rarely bilateral Underlying sinusitis can also cause periorbital swelling without cellulitis Conditions which may mimic some of the physical findings of orbital cellulitis include orbital tumors (e.g., rhabdomyosarcoma, neuroblastoma), orbital pseudotumor (an immune-mediated process), leukemia, and sickle cell crisis The best way to differentiate these mimickers of orbital cellulitis is with CT or MRI of the orbits and sinuses