Knowing how to react to someone’s illness can prove to be difficult, especially if you do not have it, or are not close to someone suffering from the disorder. Along with this, finding out that someone you know has obsessive compulsive disorder when having a conversation with them can also be extremely uncomfortable for both parties. Although you may not know what to say or do, one big thing to avoid is trying to relate yourself to OCD if you do not suffer from it.
An example of this is say the individual with OCD says that they color coordinate their closet and have to have specific hangers for specific items. When reacting to this individual, do not say something like “Oh wow, me too!”, as this could seem insensitive to them. The organization of the closet could be a part of a daily ritual that they have, and something they do not have control over. Although you may have a slightly neurotic behavior with your clothes, it is not comparable to someone with OCD who does something similar to that and it shows a serious lack of knowledge and sensitivity for the illness.
If the individual with OCD is willing and able to explain the illness to you, listen. Many have been suffering from OCD for many years and will be happy to explain it to you, as well as inform you that their medically diagnosed illness is not comparable to any habits or compulsions you may have. Be sensitive and educate yourself before you react to someone with OCD telling you about their disorder.
Resources: http://www.huffingtonpost.com/nile-cappello/living-with-ocd_b_4026119.html
http://ocd.about.com/od/glossary/g/Definition-Of-Ocd.htm