Why are children afraid of the dark?
Because the dark removes information, and a developing brain fills the gap with possibility — the fear is a normal developmental stage rather than a problem, and it typically arrives alongside the imagination that makes it possible.
Why it appears when it does. Fear of the dark generally emerges around age two to three, peaks in the preschool years, and declines through primary school. It is not present in infancy, because it requires the cognitive capacity to imagine something that is not there — the same capacity that produces pretend play and imaginary friends. It arrives as a side effect of development, not a malfunction.
Why young children cannot reason their way out of it:
The fantasy-reality boundary is genuinely under construction, and is thinner when tired, in the dark, and alone.
Explanations do not reach the fear. A child can agree that monsters are not real and remain afraid, because the reasoning and the fear are running in different systems.
Nighttime is separation, and the fear is frequently as much about being alone as about the dark itself.
What actually helps:
Take it seriously without endorsing it. "There's nothing there" dismisses; "monster spray" implicitly confirms monsters exist and need managing. Something in between works best: acknowledge the feeling, and be calmly confident about the facts.
A dim red or amber night light, which preserves sleep physiology better than blue-white light.
Predictable, unhurried bedtime routines, which reduce the arousal the fear feeds on.
Gradual practice — a parent nearby, then checking at intervals, then further away — rather than an abrupt change.
Control. A torch of their own, choosing the door position, deciding the light level.
Check the inputs. Screens, news, older siblings' games and even mild films are common triggers, and the effect frequently appears days later.
When to seek help: if fear is severe, persists well beyond the usual age range, extends beyond bedtime into daytime functioning, or comes with other significant anxiety. Fears that appear suddenly after a settled period are worth asking about gently, since something may have happened.