After helping to raise my nephew and now watching my own children develop I have come to the conclusion that once a child turns two, he or she turns into a neurotic mess.
When my nephew turned two he suddenly discovered a obsessive compulsive aversion to getting his hands dirty. He would go ballistic if so much as molecule of foreign material stuck to his hands. Finger painting (previously a favorite activity) was now out of the question.
My son is deathly afraid of fans. For him the attic fan is the Dread King of all malevolent rotary blade air circulators. The attic fan is directly over their bedroom door in the hallway. It does not even have to be on to invoke fear. So getting in and out of his room is like running a gauntlet. He also hates getting his hands dirty. Not to extent of his cousin, but it is compounded by a dire fear of baths.
My daughter is afraid of bugs in any form. She will come completely unglued at the sight of an insect that I would need a magnifying glass to even see. But she loves to play outside. She is not afraid of fans, but the vacuum cleaner terrifies her. She is afraid of the dark, but won't sleep unless she has her head burrowed under a quilt so thick that no light less than that of supernova intensity would penetrate.
I'm told that it only gets worse.