Causes of blepharitis
NHS Choices Medical Reference
Blepharitis is inflammation (redness and swelling) along the edge of your eyelids. It is most often caused by an infection or a skin condition.
There are two types of blepharitis:
- anterior blepharitis, when the inflammation affects the outside front edge of your eyelids, where your eyelashes are attached
- posterior blepharitis, when the inflammation affects your Meibomian glands (which are on the inside front edge of your eyelids and produce a fatty liquid that protects your eyes)
Sometimes, people will experience both types of blepharitis because the causes are often connected.
Many cases of anterior blepharitis are caused by a bacterial infection, usually the staphylococcus bacteria. This is known as staphylococcal blepharitis.
Anterior blepharitis is often the result of seborrhoeic dermatitis (a skin condition that causes your skin to become inflamed or flaky). As seborrhoeic dermatitis causes oily skin, it is thought that the excess oil irritates the eyelids, providing a breeding ground for bacteria. This is often referred to as seborrhoeic blepharitis and can also cause posterior blepharitis.
Posterior blepharitis is caused when something affects the Meibomian glands found on the rim of your eyelids. These are responsible for producing an oily substance that makes up the top layer of your tears and keeps your tears in place. This is often known as Meibomian blepharitis.
Skin conditions, such as seborrhoeic dermatitis and rosacea, are known to affect how these glands work.
About half of people with rosacea will experience associated eye symptoms, such as redness and irritation. Rosacea that affects the eyes is known as ocular rosacea, although this condition is unlikely to develop in people already taking oral antibiotics for rosacea.
Left untreated, ocular rosacea can lead to:
- iritis ( uveitis), inflammation of the iris (the coloured part of your eye)
- keratitis, inflammation of the cornea (the transparent outer layer of your eye)
Less commonly, blepharitis can develop as a result of: