My brother had/has OCD. It got really bad a couple of years ago. There are different types of OCD, the one my brother had forced him to wash his hands and everything around him constantly. Even the smallest touch made him uncomfortable. Everyone had to change their habits and behavior to accommodate his OCD, It really disturbed the whole family. Thankfully he seems to be over it to a large extent now.
We didn't have a doctor or therapist treat him because he refused. Anyone that has OCD needs to occupy themselves with something to take their mode off their urges. I think scientifically OCD happens due to a chemical imbalance in the brain. Don't take that as fact because I'm no expert.