[1] The swelling is due to the oozing of exudate from abnormally permeable capillaries.

In general, chemosis is a nonspecific sign of eye irritation.

The iris is not covered by this fluid and so it appears to be moved slightly inwards.

It is usually caused by allergies or viral infections, often inciting excessive eye rubbing.

Chemosis is also included in the Chandler Classification system of orbital infections.