The front part of the eye is covered by a clear dome called the cornea. This cornea gets infected with a viral disease called ocular herpes. It causes very painful sores on the surface of the eye and the eyelids. The cornea is inflamed and the eyelids also get swollen. This is very often confused with a pink eye. A patient will also suffer from mild facial swelling in the mornings when he/she awakes. However, the stickiness associated with pink eye is absent.

Those that suffer from Graves’ disease or other thyroid problems also often suffer from painful eyes and bulging eyelids. This disease causes what is known as the proptsis of the eyes. It usually affects both the eyes together and leads to reduced eye movements as well as double vision. Hypothyroidism, where the thyroid functions way below its optimum capacity, could also lead to puffiness and swelling of the eyes.

This is a serious cause of eye swelling. Cellulitis happens in two ways. Preceptal cellulitis is the result of a bacterial infection which causes pain, swelling and redness in the eyes. This usually occurs only in one eye at a time. Orbital cellulitis, however, can affect both eyes simultaneously. This is also caused by bacteria: only that they invade the sinuses in the area of the bones that make up the eye socket. Both eyes can bulge out and become painful. People suffering from orbital cellulitis often complain of pain while moving their eyes up and down.

Tears are not meant to be an emotional response alone. They also have the vital function of lubricating the eyes and protecting them from foreign bodies. At times, the tear glands do not produce sufficient tears as a result of which the eyes begin to dry. This dryness results in irritation of the eye which induces the person to rub them. The rubbing is also a reaction meant to promote tear production. But since the quantity and quality of tears are not sufficient, the eyes get red and swollen.

The eyelids have oil-producing glands for smooth functioning and lubrication. When these glands succumb to a bacterial infection, the result is a stye. It appears like a little red hump on the eyelid. It gets sore and tender. The condition is painful and may often lead to tears and wet eyes. A chalazion happens when these oil glands get blocked. The result is swollen eyes and eyelids.

Pink eye is the traditional name for what is actually known as conjunctivitis. This occurs because of the inflammation or swelling of the conjunctiva. The conjunctiva is a thin and clear mucus membrane lining the insides of the eyelid and protecting the ‘white’ portion of the eye. When this gets infected by bacteria or viruses the result can be painful. A lot of mucus gets secreted which makes the eyelids stick. Opening the eye in the morning may become difficult and will need a wash with warm water. Eyes get swollen and become itchy. A blood-red color fills the white area of the eye.

An allergy develops when the human immune system reacts adversely to a particular allergen. Eye allergies cause significant discomfort, and give rise to an intense urge to rub and scratch the eyes and eyelids. This happens because the cells located in the eyes release histamines and many other chemical substances as a defense effort against the intruding allergen. This, in turn, causes the eye to become swollen, red and watery. The eyelids also get irritable, and one experiences pain and a burning sensation in the eyes. Usually, swollen eyes due to an allergy are not contagious and this is the cause behind only one eye getting swollen.