Mara Wilson of Matilda fame now occasionally writes for Cracked. She did a piece on OCD. She's had a diagnosis for over thirteen years. She describes it better than I can.

Four Things Nobody Tells You About Having OCD.

I didn't mind Monk's portrayal, because they included facets not generally shown in the his fears.

Stottlemeyer: I thought you were afraid of heights.

Monk: Snakes trump heights. It goes, Germs, Needles, Milk, Death, Snakes, Heights, Crowds, Mushrooms, Elevators...

Stottlemeyer: Okay, okay, I don't need the entire list.

This is when I gave the show my personal blessing: fear of milk. It exists, just like my fear of satellites.