First of all, if your one of your eyes has got scratched or stung by little bugs such as a mosquito, the eye will easily get swollen. Secondly, if this eye has got in touch with something allergic or irritative, than it can also become swollen. Another reason for non-inflammatory swollen eyelid without congestion is that your eye gets angioneurotic edema. As to inflammatory swollen and painful eyelid, then maybe you get eyelid furuncle, meibomian glands, blepharitis ciliaris, and so on. You should go to the hospital to take an eye examination so as to find out the exact reason for your swollen eye in case of worse condition.
It means that there is inflammation or excess fluid in the tissues around the eye. A number of factors can lead to a swollen eye, including allergies, contact lens, stress, fatigue, crying, eye infections and eye injuries. It can also be an indication of a more serious case such as orbital cellulitis, ocular herpes. To get rid of swollen eyes, you should find out the underlying cause first. If it is caused by allergies, you can take antihistamine eye drops or oral allergy medication to help relieve symptoms. Artificial tears can also help. If it is due to infection such as conjunctivitis, you can take anti-viral or anti-inflammatory eye drops or ointments, or antibiotics. Apply cold compresses can reduce the swollen eye as well. Do not rub your eye in case of a further infection and remove your contact lenses during this phase. Ensure that you get enough sleep per day. Wish you recover soon.