Cover legend: Itch is an unpleasant sensation that evokes a desire to scratch. Many forms of chronic itch are insensitive to antihistamine treatment. The irritant receptor TRPA1 plays a key role in chronic itch. For more information, see Wilson et al. (pages 9283–9294). Cat photograph licensed and adapted from iStockphoto.com. © iStockphoto.com/fscotto74