Excessive Eye Mucus – Causes of Eye Secretions and Crusts

The production and secretion of mucus in the eyes is a continuous physiological process. The mucus in the eye is produced by the mucous membranes of the conjunctiva. Small amounts of watery mucus are secreted continuously in the eyes. This mucus thickens up as it mixes with dead skin cells, meibum (an oily substance) and tears.

Exposure to air dries the thickened mucus, which then forms a crust. The crusted and hardened mucus is most frequently visible in the corners of the eyes upon waking up in the morning. This hardened mucus crust is medically referred to as rheum. However, the rheum is better known by its common names like eye gunk, sleep dust, and eye boogers.

Normal Eye Mucus Production

The production of mucus in the eyes occurs constantly via the conjunctiva. The mucus produced by the conjunctiva mixes with meibum and tears to help keep the eyes moist. The meibum is an oily substance produced by the meibomian glands (a type of sebaceous glands) that lie within the eyelids. The tears in the eyes are produced by the lacrimal glands.

Even though the production of mucus occurs continuously in the eye, one is not aware of it as the mucus gets washed away by the blinking eyelids and tears during our waking hours. However, people who wear contact lenses may at times notice streaks of mucus on their contact lenses.

The production of tears and movement of the eyelids decrease during sleep. This causes mucus to accumulate in the corners of the eye. The accumulated mucus thickens and forms a crust. In some cases, the mucus from the eyes may also get mixed with the mucus from the nasal cavity. This is entirely normal.

Excessive Eye Mucus

Normally, mucus production and small amounts of crust formation at the corners of the eyes do not warrant any concern. Like nasal mucus, crusts of eye mucus do not usually cause any problems. Mucus in the eyes becomes a cause for concern only when its characteristics change. For example, the secreted mucus may be mixed with pus.

This type of discharge is referred to as mucopurulent discharge. Excessive production of mucus that results in blurry vision and formation of large crusts that seal the eyelids are also abnormal events that need to be investigated.

In some cases, the crusts formed by excessive mucus may be large enough to scratch the conjunctiva and cause pain. Excessive mucus production in the eyes could be a sign of some underlying medical condition that needs to be treated.

Causes of Excessive Eye Mucus

Excessive eye mucus is usually a sign of an underlying problem that needs to be identified and treated. The following are some of the possible causes of excessive eye mucus that hardens into large crests upon accumulation.

Dry eyes

Dryness of eyes occurs when the secretion of tears reduces. In the absence of a sufficient flow of tears, mucus accumulates in the eyes instead of being washed off. Dry eyes are also prone to getting injured or infected. An eye injury or infection can worsen the mucus secretion further.

Dry eyes are characterized by symptoms such as redness in the eyes, a gritty sensation in the eyes, eye pain, and stringy or watery mucus in the eyes. The dryness in the eyes can either be temporary or persistent. Temporary dryness in the eyes could be due to dry weather conditions or certain lifestyle factors.

Persistently dry eyes can result from a number of causes, including reduced secretion of tears in old age, hormonal changes, deficiency of vitamin A, continuous eye strain, side-effects of drugs such as antidepressants and antihistamines, blocked tear duct, thyroid disorders, diabetes mellitus, contact lenses and refractive eye surgery.

Infectious conjunctivitis

The term “conjunctivitis” refers to an inflammation of the conjunctiva membrane that covers the eyes and the inside portion of the eyelids. Some of the main signs and symptoms of conjunctivitis are significant redness in the eyes, swollen eyes, burning sensation in the eyes, itchy eyes, gritty sensation in the eyes, eye pain, and mucopurulent discharge from the eyes.

Read more on conjunctivitis.

Due to the extensive redness of the eyes in conjunctivitis, the condition is also commonly referred to as the pink eye. The most common cause of conjunctivitis is a viral infection of the eyes. Bacteria and fungi may also cause conjunctivitis in some cases. When the infection in conjunctivitis spreads to the cornea, the condition is referred to as infectious keratitis.

Allergic conjunctivitis

Conjunctivitis is not always caused by an infection. It could also be a result of an allergic reaction in susceptible individuals. Allergic conjunctivitis refers to an inflammation of the conjunctiva due to an abnormal immune response to a harmless substance in the eye. The symptoms of allergic conjunctivitis are similar to infectious conjunctivitis.

For example, individuals suffering from allergic conjunctivitis display signs and symptoms such as red and swollen eyes, gritty feeling in the eyes, stringy or watery mucus in the eyes, and severe itching in the eyes. However, they also display other symptoms that are typical of an allergic reaction, such as runny nose, nasal congestion, and persistent sneezing.

Individuals who suffer from other allergic conditions such as hay fever are more likely to get affected by allergic conjunctivitis compared to individuals who do not have any allergies.


Blepharitis is a medical term that refers to an inflammatory reaction in the eyelids. The inflammation in blepharitis may also extend to the conjunctiva and the meibomian glands in the eyelids.

Common signs and symptoms of blepharitis include swelling of the eyelids, soreness in the eyelids, excessive tear and mucus secretion in the eyes, formation of eye crusts, presence of sticky mucus in the eyes, itching in the eyes, gritty feeling in the eyes, sensitivity to light, and redness in the eyes. The movements of the eyelids may also get affected due to the inflammation in blepharitis.


A stye is an infection of the oil glands in the eyelids by a bacterium known as Staphylococcus aureus. One of the characteristic features of stye is the appearance of a red, painful bump or pimple on the edge of the eyelid. The eyelid itself may swell and become painful.

The eyes may become dry and red. Excessive secretion of tears and mucus also occurs, leading to the formation of crusts over the eyelids. The red bump on the eyelid may also have pus in it. In most cases, stye resolves on its own without treatment. In some cases, however, a stye may persist and require medical treatment to prevent complications.

Preventing excessive eye mucus

In most cases, excessive mucus can be wiped or cleaned with water and soap. However, one should not try forced removal of mucus crusts that are large, hard, and difficult to remove. Doing so may cause eye injury. It is best to consult a doctor in such cases. In addition to removal of hard and large mucus crusts, one must also identify and treat the underlying condition that is causing excessive mucus in the eye.

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