Swollen eyelids cause a puffy appearance to the eyes. Causes of swollen eyelids include fluid retention, allergies, eye infections and eye injuries. Virtually any cause of inflammation to the eye area may manifest as eyelid swelling, although allergic reactions are likely the most common cause. With allergic reactions, the eyes may also be red, itchy as well as swollen. Sometimes the swelling may be below the eyes on both sides.

A swollen eyelid is usually a symptom, not a condition. It's very common and is usually due to allergy, inflammation, infection, or injury. The skin of your eyelid is less than one milli meter thick. But, since the tissue is loose and stretchy, your eyelid is capable of swelling considerably.

Several reasons your eyelid may be swollen include:
1.allergies
2.a bug bite
3.fluid retention
4.pink eye (conjunctivitis)
5.a chalazion, which is a blocked oil gland that’s commonly referred to as a stye
6.periorbital or orbital cellulitis, which is inflammation that spreads to the skin around your eyes
7.trauma or injury, which is often accompanied by discolouration
8.lack of sleep
Some medical conditions can also cause symptoms of a swollen eye or eyelid.