Contact urticaria and the environment.

The environment is defined by the aggregate of surrounding things, conditions, or influences. The biophysical environment includes the physical and biological factors, along with chemical interactions that affect an organism. Contact dermatitis includes any inflammatory skin reaction to direct or indirect contact with noxious agents in the environment. Although the main clinical expression of contact dermatitis is eczema, other expressions like urticaria, contact urticaria (CoU), or lichenoid eruptions are described. The main objective of this chapter is to review CoU, which is often misdiagnosed, as part of the CoU syndrome (CUS).