Matchbox sign is a psychiatric finding. Patients with delusional parasitosis often arrive at the doctor's office with what healthcare professionals call the matchbox sign, a medical sign characterized by the patient making collections of fibers and other foreign objects supposedly retrieved from the skin. The name refers to the fact that such collections can be stored in matchboxes or other similar small containers, which are then presented to the patient's physician.
References
Matchbox sign Wikipedia(Text) CC BY-SA