Sleep Crust
Many people notice a gritty or sticky crust in the corners of their eyes when they wake up. This is often called “sleep crust” or “eye discharge,” and it happens because the eyes stay still and do not blink during sleep. Sleep crust forms as a mix of mucus, oils, skin cells, and tiny debris that collect while the eyes rest.
While this is a normal part of eye health, the amount, texture, or timing of discharge can sometimes point to other issues. Conditions such as blepharitis, conjunctivitis, or dry eye can lead to more frequent or bothersome buildup. In other cases, simple factors like allergies or dust may cause temporary changes without signaling disease.
Definition of Symptom
Sleep crust, also called eye discharge or rheum, is the dried or sticky material that builds up in the corners of the eyes. It often appears after waking and is sometimes referred to as eye gunk or crusty eyes in the morning. The eyes produce a mix of mucus, oils, skin cells, and tears.
Blinking during the day clears these materials away, but at night, without blinking, they collect along the lash line and near the tear ducts. The tear film helps protect the eye surface and keep it moist. If tear production changes, the amount of discharge may also change.
The meibomian glands in the eyelids release oils that keep tears from evaporating too quickly. When these oils combine with mucus and natural debris, they can dry into crust by morning. In most cases, sleep crust is normal. It may look dry and flaky or wet and sticky, depending on how much moisture remains in the discharge.
| Term | Description |
|---|---|
| Rheum | Eye discharge. |
| Tear Film | Protective layer covering the eye. |
| Meibomian Glands | Oil-producing glands in eyelids. |
| Conjunctiva | Thin tissue lining the inside of eyelids and covering the white of the eye. |
Usually harmless, changes in color, texture, or amount of discharge may signal irritation or another eye condition.
Possible Causes/Diseases Condition
Sleep crust forms when mucus, oils, and skin cells collect at the corners of the eyes during sleep. While a small amount is normal, excessive eye crust can signal an underlying condition. Common causes include:
- Blepharitis: Inflammation of the eyelids that leads to redness, irritation, and sticky discharge.
- Conjunctivitis: Also known as pink eye, this condition can be viral, bacterial, or allergic, often causing thick or watery discharge.
- Blocked Tear Ducts: When tears cannot drain properly, mucus builds up and dries into crust.
- Styes: Small bumps on the eyelid caused by blocked oil glands that may produce pus or crust.
Bacterial conjunctivitis often creates yellow or green discharge that dries into crust. Viral conjunctivitis usually causes watery discharge that can still leave behind crust along the lashes. Dry eyes may also contribute. When the eye surface lacks enough moisture, it can trigger extra mucus production, which later hardens into crust. Allergies often have a similar effect, producing watery discharge that dries overnight.
| Condition | Typical Signs | Discharge Type |
|---|---|---|
| Blepharitis | Red, swollen eyelids | Sticky, flaky crust |
| Bacterial Conjunctivitis | Red eye, irritation | Thick yellow/green |
| Viral Conjunctivitis | Watery, itchy eyes | Clear, watery crust |
| Blocked Tear Duct | Excess tearing, swelling | Mucus buildup |
| Stye | Painful eyelid bump | Pus, crusty edges |
Other Non-Disease Causes
Not all eye crust comes from infection or illness. Everyday factors can affect the eyes while a person sleeps and lead to crust.
- Dry eye is one of the most common reasons. When the eyes do not produce enough tears, they may release thicker mucus that dries overnight and forms crust.
- Allergies also play a role. Seasonal allergies from pollen or indoor triggers like pet dander can cause the body to release histamine. This reaction often leads to watery, itchy eyes that produce more discharge.
- Environmental factors such as dust in the bedroom can irritate the eyes. Even small particles may cause extra tearing and mucus buildup during sleep.
- Wearing contact lenses for long hours, or not cleaning them well, can leave the eyes more prone to irritation. This can increase the amount of discharge that collects at the corners of the eyes.
A quick overview of common non-disease causes:
| Cause | Effect on Eyes | Possible Result |
|---|---|---|
| Dry eye | Reduced tear film | Thicker mucus, crust buildup |
| Allergies | Histamine release, eye irritation | Watery eyes, extra discharge |
| Dust | Irritation from particles | Mild tearing, crust formation |
| Contact lenses | Eye surface irritation | More mucus during sleep |
These factors are usually temporary and improve when the trigger is reduced or removed.
How It Causes the Symptom
When a person sleeps, the eyes stop blinking. Blinking usually clears away mucus, oils, and tiny debris during the day. Without this natural rinse, these materials collect in the corners of the eyes. Tear production also slows during sleep. With less moisture, the discharge can dry and form small crusts. This is why the buildup is most noticeable in the morning.
Main Contributors to Sleep Crust
- Mucus from the tear film
- Oils from the eyelid glands
- Dead skin cells
- Dust or small particles
Poor eyelid hygiene or inflamed eyelid margins can increase buildup. Blepharitis can make the discharge thicker and more frequent.
Possible Complications
Mild sleep crust is usually harmless, but certain symptoms can point to underlying problems. Thick, colored discharge or discharge that happens throughout the day may signal an infection or another eye condition. Common warning signs include:
- Eye pain or discomfort
- Light sensitivity
- Blurry vision
- Persistent watery eyes
- Eye redness
These symptoms may suggest issues such as blepharitis, conjunctivitis, or dry eye. Infections can spread if untreated, leading to more irritation and swelling. A more serious complication is a corneal ulcer, which is an open sore on the surface of the eye. This condition can cause severe pain, redness, and vision changes. Without care, it may result in lasting damage.
| Symptom | Possible Concern |
|---|---|
| Eye pain | Infection or corneal ulcer. |
| Light sensitivity | Inflammation or corneal damage. |
| Blurry vision | Severe dryness or infection. |
| Watery eyes | Allergies or blocked ducts. |
| Eye redness | Conjunctivitis or irritation. |
When to Seek Medical Attention
Most people notice a small amount of sleep crust in the morning, which is normal. But certain changes in the discharge or other symptoms can suggest a problem that needs medical care. Signs that require attention include:
- Thick, green, or dark yellow discharge.
- Crust that makes it hard to open the eyes.
- Eye pain, swelling, or redness.
- Sensitivity to light or blurred vision.
- Fever or other signs of illness.
If you notice these symptoms, contact an eye doctor. An optometrist can do an initial exam, but you may need an ophthalmologist for more complex cases or if an infection is likely.
| Situation | Who to See |
|---|---|
| Mild irritation, dryness, or allergies | Optometrist |
| Persistent or worsening discharge | Optometrist or Ophthalmologist |
| Severe pain, swelling, or vision changes | Ophthalmologist |
Gently cleaning your eyelids with a warm cloth may help with minor crust. If symptoms do not improve or get worse, seek professional care.
