From a leading figure in the field of psychotherapy, this new book is the first dedicated to the topic of the fear of contamination. The fear of contamination is the driving force behind compulsive washing, the most common manifestation of obsessive compulsive disorder. It is one of the most extraordinary of all human fears. People who have an abnormally elevated fear of contamination over-estimate the probability and the potential seriousness of becoming contaminated. They believe that they are more susceptible than other people to contamination. People who labour under the illusion that they are particularly vulnerable to contamination are persistently anxious, excessively vigilant and highly avoidant.The fear is complex, powerful, probably universal, easily provoked, intense, and difficult to control. Usually it is caused by physical contact with a contaminant and spreads rapidly and widely. When a person feels contaminated it drives a strong urge to remove the contamination, usually by washing. The fear and subsequent urges over-ride other behaviour. A fear of contamination can also be established mentally and without physical contact. The fear can arise after exposure to violation, physical or non-physical, and from self-contamination. The book starts by defining the disorder, before considering the various manifestations of this fear, examining both mental contamination and contact contamination, and feelings of disgust. Most significantly, it develops a theory for how this problem can be treated, providing clinical guidelines - based around cognitive behavioural techniques.