Orbital and periorbital cellulitis are usually caused by infection of the sinuses near the nose. Insect bites or injuries that break the skin cause about one-third of these cellulitis infections. Orbital and periorbital cellulitis may also occur in people with a history of dental infections.

The blood of about 33 of every 100 patients with orbital or periorbital cellulitis contains bacteria known to cause:

• acute ear infections
• inflammation of the epiglottis (the cartilage flap that covers the opening of the windpipe during swallowing)
• meningitis (inflammation of the membranes that enclose and protect the brain)
• pneumonia
• sinus infection.

People with periorbital cellulitis will have swollen, painful lids and redness, but probably no fever. About one child in five has a runny nose, and 20% have conjunctivitis. Conjunctivitis, also called pinkeye, is an inflammation of the mucous membrane that lines the eyelid and covers the front white part of the eye. It can be caused by allergy, irritation, or bacterial or viral infection.

As well as a swollen lid, other symptoms of orbital cellulitis include:

• bulging or displacement of the eyeball (proptosis)
• Chemosis (swelling of the mucous membrane of the eyeball and eyelid as a result of infection, injury, or systemic disorders like anemia or kidney disease)
• diminished ability to see clearly
• eye pain
• fever
• paralysis of nerves that control eye movements (ophthalmoplegia)