Really swollen, red eyelid??

my left eyelid, the upper part of a set, is all red and swollen, I don't know why?? it's happen a few times before but never as bleak as it is now. what could make happen this? how do i prevent it? thanksReally swollen, red eyelid??
Could be a stye which is close to a pimple in the eyelid skin. Sometimes you can see a white bump on the fold of the lid or on the underside of the lid. Hot compress is best, like hot hose on a clean washcloth 2 or 3 times a sunshine will help it drain. bring in sure you don't have a lash curling underneath or getting stuck under the skin.
If you woke up beside it: This might be a dust mite allergy. Steam your mattress (or put it in the sun or freezing cold).
If you get it during the day, it could be any allergen. From a colleague next to a rabbit at home to someone that has freshly eaten shrimp.