von Frey hairs: new materials for a new design.

von Frey filaments are widely used in pain research. Conventionally, they are made of synthetic fibres. This plastic material is susceptible to changes in humidity and temperature, and such filaments do not keep their calibration. Filaments made of optical glass fibres are highly elastic and do not suffer these problems. Their optical properties can be used to make thin fibres more visible. Copyright 2001 European Federation of Chapters of the International Association for the Study of Pain.