Question

Which humour comes out of our eyes when we cut onions and which when we don't blink our eyes and keep them open for a long time?

Answer 1

When an onion is cut it produces a compound(Lachrymatory-factor synthase) that irritates the lachrymal glands in the eyes and cause them to water.An enzyme in the onion spurs the production of the irritating compound.

Blinking is essential movement that helps moisturized our eyes.

Human has lacrimal glands located just near eyes. This gland secretes tears which contain antibodies, lysozymes, electrolytes, water, etc. Blinking helps spreading this “tears” on the surface of the eyes (cornea and conjunctiva).

If somebody didn’t blink for a substantial amount of time or suffering from disease that impair the closure of the eye (e.g bells palsy) then the surface of our eyes will be dried. This is known as xerophtalmia. This will damage the surface of our eyes (cornea and conjungtiva).