Why do we have red colour eye after crying ?

First  , why do eyes get red ? The tissues of eyes need oxygen and nutrients . They have blood supplying vessels . When our eyes are at their usual white  , these blood vessels are not dilated . When our eyes become red  , these blood vessels become dilated . Hence the redness i.e. the blood vessels become visible compared to the usual white background of eye .


Lacrimal glands are responsible for keeping our eyes moist . Extra secretion of fluid from these glands results in tears . When we cry , the blood vessels to these glands become dilated so that to provide extra nutrients to these glands .

The increased blood flow in these dilated blood vessels around the eye is responsible for the redness of the eyes .