My wife's close friend has a husband who is I suspect OCD.
Our house is not especially tidy or modern, but it's not like something out of How Clean Is Your House - we do wash up daily, but there toys on the floor, and letters not filed from 3 weeks ago by the door.
Anyway, wife's friend lives in a brand new house and her husband appears to have some sort of OCD. He just came back from with his wife and kids (wife is from ), and apparently he ate lots in the luxury hotel at breakfast buffet than ate nothing else all day, refusing to eat food cooked by m-i-l whom they visited each day. Ok, hygiene standards are much lower over there, but still.
Anyway, they dropped by unannounced to drop off some gifts they'd brought back, I invited them in and called my wife to say that they were here. (She had gone shopping locally.) She came back later, after they had gone, and said she didn't want to be in the house with him because the last time he had been here, she had witnessed him opening our front door using a tissue, when he thought nobody was watching.
My wife had noticed this and was deeply offended and thought it very rude (hadn't said anything to him about it).
I said to her 'that's not normal behaviour, it's mental illness, have some understanding, he's not being rude he's just OCD or something'.
The husband is always polite and quite friendly, so I don't see that my DW should be offended by him opening our front door with a tissue when nobody was watching. Ok, he obviously thinks our house is unsanitary, but that's his problem not ours....