Children sometimes pick their noses and eat what they find.
Science does not have one proven universal explanation for why.
Curiosity is probably part of it
Young children investigate the world through touch and taste.
They also have fewer social rules firmly installed.
Something that adults immediately label disgusting may simply be interesting to a child.
Habit can take over
A behavior that starts from curiosity can become automatic.
Nose picking may happen during boredom, concentration, stress, or television watching.
Once the material is on a finger, eating it may become part of the same habit.
The taste and texture may matter
Mucus contains water, salts, proteins, cells, and trapped material.
Some children may simply find the salty taste or texture interesting.
That does not mean the behavior has a hidden nutritional purpose.
Is there a health benefit?
Claims that eating boogers deliberately trains the immune system go beyond the evidence.
Your immune system already encounters microbes constantly.
There is no medical need to add nose contents to the menu.
What are boogers anyway?
Boogers form when nasal mucus traps particles and then dries.
So the material is basically used air-filter material from the nose.
Not exactly a culinary recommendation.
Should parents panic?
Occasional nose picking is extremely common in children.
The bigger concerns are injury from aggressive picking, nosebleeds, or a compulsive habit that causes problems.
There is no elegant scientific answer.
Sometimes the explanation may simply be that it was there.
And that’s the short explanation.
Related explanations: Why do boogers form?, Why does your nose get stuffy?, and Why does morning breath smell?