A black eye is most commonly caused by something hitting the eye or nose. Either one or both eyes may be blackened depending on where you get hit. If you suffer a blow to the nose, both eyes may swell; the swelling is due to the buildup of fluid in the loose skin beneath the eyes. Other types of trauma to the head can cause black eyes, including skull fractures.
Facial surgery can also cause black and swollen eyes, including facelifts, nose surgery or surgery on the jaw. Other conditions, such as allergies and infections, can lead to swelling around the eye, but not the bruising discoloration of a black eye.
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