Hello, I work in the medical industry in a role that requires me to read patient's medical records.

I have come across at least 8 over the 15 years I have been in this profession patients that truly believe that they have 'worms' inside their body to the point of ingesting large amounts of diatomaceous earth, stuffing this in body cavities, commonly attempting (sometimes believing that they have been successful) to trap one of the parasites in a container. The parasite is never there when they see the doctor.

Why is this such a common delusion? All the patients I encountered who believed that they were infested had almost identical descriptions and acted very similarly, I.e attempting to catch a specimen, threatening suicide, ingesting substances that they thought would destroy the parasite. Is there a particular condition that causes these symptoms?