We’ve all experienced it: waking up with a sticky, yellowish substance in the corner of our eyes. Most of us colloquially call it “sleep,” but in medicine, it’s more commonly referred to as eye discharge . It’s harmless (we all experience the same thing), but the truth behind it is both fascinating and somewhat unsettling.
According to neuroscientist Dr. Andrew Huberman, this embedded substance is actually a mixture of mucus, natural oils, dead cells, and… wait for it… dead bacteria. That’s right. That yellow mucus? It’s from the first few days of the day when the immune system is working simultaneously.
It was over, what did that mean?
During the day, blinking is like a windshield wiper: it constantly cleans and lubricates everything. After a night’s sleep, when we see the next moment, we hear it and wait to see it. Without these regular rinsings, all the debris removed by the eyes during the day—dust, pollen, bacteria—accumulates.
At night, your immune system is activated. It can exploit bacteria and environmental stimuli, if they are already active. The result? Dead white blood cells, bacteria, and other debris accumulate and form a yellow crust. Dr. Huberman describes it as a “war casualty”: your immune system stands guard while you sleep
