This is mainly done in real life situations after carefully informing (educating) the patient about obsessive compulsive disorder and the pros and cons of this method and preparation of the therapeutic process.
Client exposure to the things (or thoughts) that cause anxiety or catastrophical thoughts is repeated until the client feels a marked relief of the anxiety symptoms. One common example for a client with contamination fears would be to force exposure to dirty or germy objects. This must cause symptoms of anxiety and severe distress for the client. But the client will also experience that no catastrophic event will follow this exposure, and that after a period of about 30 minutes (sometimes much longer) a decrease of anxiety symptoms occurs. This procedure has to be repeated several times with different objects or levels of fear.
Without this therapy approach a client would try to perform rituals to clean their hands or body with a lot of repetitions (like washing hands or taking showers). Response prevention will stop and prevent this behaviour. Once again the client will experience anxiety and severe discomfort. But the negative feelings will decrease and no severe negative consequences will follow. Many clients believe they might go crazy if they are not allowed to perform their obsessive-compulsive rituals. No doubt: They might feel very disturbed and nervous but they will not go crazy. This is a very good and important experience that helps the patient to face more situations which caused obsessive-compulsive behaviour.
This technique is very effective. There is a marked reduction of symptoms in about 50-80 % of the clients after 20 cognitive behavioural session. Many clients will continue to have milder obsessive-compulsive symptoms, but these symptoms do not interfere with normal living.