The evidence is obscure. Small packages and letters are brought in, allegedly containing animals, but which on closer inspection turn out to be crumbs, wool scraps, skin flakes, scabs, boogers etc. In addition, are suspicious out garments and furniture, which do not contain the alleged animals either. Bare skin surfaces are displayed, especially the forearms, which can be more or less scarified or bear traces of attempts to operate the animals out. However, they lack the marks of bites, which are usually associated with insects and mites.

The animals are unusual. For example, these may be animals biting shards of the china, animals that change color, shape and properties of very fast (white animals that fly and the next moment stick to bathroom tiles like small black dots that will not come off). They can also be animals that pierce through the skin on the forearms, animals that gnaw holes in the freshly washed clothes and old plastic bags and above all animals that for a long time have resisted plenty of insecticides. Animals that are new to science or of exotic origin are not lacking in these delusions either.

Felt in the hair. Itching and biting is felt, as well as the feeling of something crawling on arms, legs and especially in the hair. The symptoms culminate when the person is at rest.

Cleaning mania. Often, treatment with insecticides as well as cleaning the house is wildly exaggerated. These are powerful things that are used on furniture and skin: lye, kerosene, alcohol, ammonia, chlorine, etc. and poison is dusted and sprayed. If there is a dog or cat, it gets its share and if these are the ones to fall under suspicion, it is not unusual that the patient have them put down by the vet.

Women over 45. It is mainly in middle-aged and older women that the symptoms of delusional parasitosis are seen. In men and younger women, the disease is not so common.

Delusions of infection. Patients often express that they have been infected on a particular occasion, have acquired the infection from certain people or pets, from dirty sheets etc. They are convinced that they can infect others, are very concerned about avoiding infecting their immediate family and are afraid to go out in public. Above all, neighbors and friends must not discover that patients are carriers. The animals can also be infectious, but on another level. It happens in people living together that the sick have the healthy forced into their universe after which they both confirm each other’s delusions. The phenomenon is called “folie à deux”.

Lack of logic. The sick can discuss their own situation more or less rationally, but cannot by logical arguments be persuaded to depart from the perception that animals are the case. Typically the comment is: Well, if it is not animals, then why do they (the animals) bite me. The correct perception that it is a case of mental illness, the patient will not accept at all and will of course do not seek psychiatric help either.