Delusional parasitosis (DP) is a somatic type of delusional disorder, usually mono-symptomatic, in which the patients are convinced they are being infested with animal parasites while no objective evidence exists to support this belief. The complaints are usually about skin infestation, but involvement of the gastrointestinal tract has also been described. Numerous samples are brought for examination from skin, clothes, and environmental sources, while a detailed description of the “parasite” is given. In primary DP, the delusion arises spontaneously as a mono-delusional disorder, while in secondary DP, the delusional disorder arises secondary to another major medical, neurological, or psychiatric disorder. Practically all patients refuse psychiatric help. Shared psychotic disorder – folie à deux – is a known mode of presentation in delusional parasitosis. More than one member within a family may experience the same delusional state. For diagnosis and treatment of DP, a close collaboration among dermatologists, psychiatrists, and parasitologists is essential. Patients whose delusion of parasitosis is not severe can sometimes be relieved of their symptoms by establishing a reliable and meaningful therapeutic relationship. Symptomatic medication may be prescribed for the relief of pruritus, pain, and other symptoms. In more severe cases, such patients should be treated with psychopharmacological agents.