Abrasion play involves sexual arousal from contact with abrasive substances. Usually, a Dominant will interact with a submissive/slave using a harsh rubbing of the skin known as a 'Dutch rub ' and make use of various substances such as scratchy wool, sandpaper, emery boards, etc. While some materials like sandpaper and steel wool may cause lasting injury, they can and are still used. Another form of abrasion play is "birching", where a person is hit or brushed with handfuls of twigs and leaves. Abrasion play is generally considered safe as long as the skin is not broken. If the skin is broken, even in tiny areas, the area should be disinfected and protected as with any open wound to prevent infection. Improper care can result in permanent scarring. Each person has a different pain threshold with some being able to handle harder and more abrasive play than others.