1. What is sleep crust?
Sleep crust, medically known as rheum, is a natural accumulation of mucus, oils, skin cells, and debris that gathers at the corners of your eyes during sleep. This yellowish or whitish crust serves as a byproduct of the eye’s continuous cleaning and protective mechanisms while you rest. It acts as a barrier to trap dust, bacteria, and other microscopic particles, preventing them from irritating the eye’s surface.
Although it might seem unpleasant, sleep crust is essentially a sign that your eyes are functioning properly, producing tears and other secretions to maintain ocular health. The color and texture can vary depending on factors such as hydration, tear production, and environmental conditions.
2. How sleep crust forms
During waking hours, blinking spreads tears evenly over the eye’s surface, washing away impurities and excess secretions. The eyelids act like windshield wipers, clearing away mucus, dust, and dead cells. However, when you sleep, blinking stops or significantly decreases, causing these secretions to accumulate.
As these substances build up without being wiped away, they dry and form the visible crust in the inner and outer corners of your eyes. Individuals with conditions like allergies or excessive tear production may notice more pronounced sleep crust, especially during seasonal changes or exposure to irritants.
The rheum consists of:
- Mucus from the conjunctiva and cornea
- Oils from the meibomian glands in the eyelids
- Dead skin cells and debris
- Microbial waste products
