Waking up to find your eyelids glued together by a sticky discharge can be an alarming start to the day. This common phenomenon is often called “sleep crust,” but its scientific name is rheum. Rheum is the accumulation of natural substances. While it might temporarily seal your eyes shut, it is generally a harmless byproduct of the body’s protective processes. Understanding why this discharge collects overnight can help demystify this morning experience.
The Composition of Sleep Crust
The eye continuously produces the tear film, a protective layer that keeps the surface clean and moist. Sleep crust is the dried residue of this tear film mixed with debris collected throughout the day. It is composed of mucus, which is discharged from the conjunctiva, the thin membrane lining the inside of the eyelids and the white part of the eye.
The discharge also contains oils, specifically meibum, secreted by the meibomian glands along the eyelid margins. These oils prevent the tear film from evaporating too quickly, but they can solidify and mix with the mucus during sleep. Exfoliated skin cells and stray dust particles are also trapped in this sticky mixture.
During waking hours, blinking washes this material into the tear drainage system. Since blinking stops during sleep, the debris collects in the inner and outer corners of the eye. The liquid components evaporate, leaving behind the hardened crust that seals the eyelids shut. Normal rheum is typically white or a light cream color.
Factors Contributing to Excessive Stickiness
While a small amount of sleep crust is normal, increased volume or stickiness often indicates an underlying condition. Dry eye syndrome is a common culprit, as reduced tear production overnight allows mucus to thicken and become more viscous. Environmental factors, such as sleeping near a fan or air vent, can exacerbate dryness and lead to a greater build-up of discharge.
Seasonal allergies, or allergic conjunctivitis, can cause the eyes to produce excessive, watery discharge that dries into a sticky film. A more concerning cause is an infection, such as bacterial or viral conjunctivitis (pink eye). Viral conjunctivitis typically results in watery discharge with morning crusting. Bacterial infection usually produces a constant, thick, yellow or greenish pus-like discharge.
The inflammation of the eyelids, called blepharitis, is another factor that causes significant crusting along the lash line. This condition is often related to blockages of the meibomian glands or an overgrowth of bacteria. The stickiness in these cases results from the eye attempting to flush out irritants or fight infection.
Safe Techniques for Opening and Cleaning
The safest way to deal with stuck eyelids is to avoid rubbing them open with dry fingers. Rubbing can introduce bacteria from your hands and further irritate the delicate eye tissue. Always begin the cleaning process by thoroughly washing your hands with soap and water.
Next, apply a warm compress to the closed eyelids to loosen the dried discharge. Soak a clean washcloth in warm—not hot—water and hold it over your eyes for a few minutes. The gentle warmth rehydrates the crust, making it soft and easier to remove without pulling on the skin or eyelashes.
After the crust has softened, gently wipe the discharge away using the washcloth or a clean cotton pad. Always wipe in a direction moving away from the eye’s surface, usually from the inner corner outward. If you suspect an infection in one eye, use a separate, fresh cloth for the other eye to prevent spreading contagions.
Warning Signs Requiring a Doctor’s Visit
While mild stickiness is normal, certain symptoms indicate a problem requiring professional medical attention. If the discharge suddenly becomes thick and changes color to yellow, green, or gray, it may signal a bacterial infection needing prescription treatment. Similarly, if the amount of discharge is so excessive that it prevents opening your eyes even after cleaning, you should see an eye care professional.
Other red flags include eye pain, a sudden increase in light sensitivity (photophobia), or noticeable changes to your vision, such as blurriness. If the eyelid or the area around the eye becomes significantly swollen or tender, or if the symptoms worsen rapidly, seek prompt evaluation. If symptoms fail to improve after 24 to 48 hours of diligent self-care, a doctor’s visit is warranted to rule out more serious conditions.