This is an infection of the skin around the eye. The cause for cellulitis is sometimes obvious – a scratch on the skin or bug bite becomes infected. Many times, however, the initial insult is not discovered. A cellulitis infection spreads under the skin and causes skin redness, heat, and impressive eyelid swelling. When isolated to the superficial layers of skin, this type of infection is generally minor and is treated with oral antibiotics and careful monitoring. If the infection penetrates deeper through the septum layer of the eyelid, than the eyeball and ocular muscles can be involved. This is called post-septal or “orbital” cellulitis. This deeper infection is serious and usually warrants hospitalization, IV antibiotics, and potentially, abscess drainage.