Pugs have two distinct shapes for their ears, 'rose' and 'button'. 'Rose' ears are smaller than the standard style of 'button' ears, and are folded with the front edge against the side of the head. Breeding preference goes to 'button' style ears. Eye prolapse is a common problem among Pugs and other brachycephalic breeds (see brachycephalic airway obstructive syndrome) and can be caused by a trauma to the head or neck, or even by the owner using a tight leash instead of a harness. Pugs have many wrinkles in their faces, so owners will often clean inside the creases to avoid irritation and infection. If this is not done, the dog may develop a condition known as skin fold dermatitis.