Delusional Infestation: A View from Europe

Delusional infestation (DI) is a relatively rare delusional disorder. People with DI characteristically have a fixed belief that they or their immediate environment is infested with insects, parasites, inanimate objects or small living creatures. This is in the absence of medical evidence for such an infestation. Patients often believe that the infestation is on or underneath their skin, in their whole body or in their immediate environment. This could entail anything from bedding or clothes and the entire house to their surroundings. The characteristic hallmark of a delusion is that the belief of being infested is held with a high degree of certainty. This is called delusional intensity in psychiatry; it can only be shifted temporarily, if at all. The evidence put forward by a patient with DI is usually not logical or in keeping with real infestations. In its long history, DI has been known under numerous terms. The most famous name is Ekbom syndrome, named after the Swedish psychiatrist who coined the German phrase Dermatozoenwahn back in the 1920s. Amongst numerous different terms that have been used in the last three centuries to describe this illness, the most common one until recently was delusional parasitosis. Since 2010, the term delusional infestation has been used and is now the most widespread term because it leaves room for any future type of alleged pathogen.