Common causes of swollen eyes include infections, injuries, trauma and allergies. Swelling specific to the eyelid is sometimes a result of more serious issues, such as orbital cellulitis, Graves' disease and ocular herpes, according to AllAboutVision.com.
Conjunctivitis is one example of a common eye infection. Also referred to as pinkeye, this infection causes inflammation in the clear lining on the surface of the eye, explains AllAboutVision.com. Other symptoms of this infection include itchiness and red, watery eyes.
Different types of injuries that can affect the eyes include insect bites, burns and foreign objects entering the eyes, reports WebMD. Trauma caused by eye surgeries can also trigger inflammation, notes AllAboutVision.com. Pollen, dust, pet dander and some eye drops or contact lenses commonly bring on allergic reactions in the eyes. Makeup also sometimes causes allergic reactions that trigger inflammation.
When the eyes have an allergic reaction, they release chemicals that help protect them from foreign objects. Histamine is the most common chemical released in allergic reactions, and it causes the blood vessels in the eyes to swell, explains AllAboutVision.com. It also causes the mucous membranes to become irritated and itchy. Additional symptoms associated with swollen eyes include excess tear production, obstructed vision and eye discharge.