Blepharitis is inflammation (redness and swelling) along the edge of your eyelids. 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.
Anterior blepharitis Causes
Many cases of anterior blepharitis are caused by a bacterial infection, usually, a staphylococcal infection that is caused by the staphylococcus bacteria. Blepharitis that is caused by this type of bacteria is often known as staphylococcal blepharitis.
Anterior blepharitis can also occur as a complication of seborrhoeic dermatitis (a skin condition that causes your skin to become inflamed or flaky). As seborrhoeic dermatitis is known to cause oily skin, it is thought that the excess oil can irritate the eyelids, providing a breeding ground for bacteria.
Blepharitis that is caused by seborrhoeic dermatitis is often referred to as seborrhoeic blepharitis. It often occurs with posterior blepharitis as well.
Posterior blepharitis Causes
Posterior blepharitis is caused when something affects the Meibomian glands that are found on the rim of your eyelids. These glands are responsible for producing an oily substance that makes up the top layer of your tears. This oily substance is needed to keep your tears in place and protect your eyes.
Blepharitis that is caused by problems with the Meibomian glands is often known as Meibomian blepharitis.
Skin conditions, such as seborrhoeic dermatitis and rosacea (a skin condition that mainly affects the face), are known to affect how these glands work.
Seborrhoeic dermatitis Causes
In the case of seborrhoeic dermatitis, the glands produce too much oil. As with anterior blepharitis, the excess oil is thought to provide a breeding ground for bacteria.
In the case of rosacea, not enough oil is produced. However, this is still a problem because your eyes are not being properly protected by your tears, so they also become vulnerable to infection.
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 colored part of your eye)
- keratitis, inflammation of the cornea (the transparent outer layer of your eye)
See the Health A-Z topic about Rosacea for more information about this condition.
Other blepharitis causes
Less commonly, blepharitis can develop as a result of:
- an allergic reaction
- an infestation of lice on the eyelashes
Allergy is the term used to describe an adverse (bad) reaction that the body has to a particular substance.
Antibiotics are medicines that can be used to treat infections caused by micro-organisms, usually bacteria or fungi.
Bacteria are tiny, single-celled organisms that live in the body. Some can cause illness and disease and some are good for you.
Inflammation is the body’s response to infection, irritation or injury, which causes redness, swelling, pain and sometimes a feeling of heat in the affected area.
The Meibomian glands are located on the inside front edge of your eyelids. They produce a fatty liquid that makes up the outer layer of the tear film and protects your eyes.