Fear play is typically considered edge play, a category of BDSM related activities with high physical and/or psychological risk. The exact practices vary widely depending the individual participants. Limits are considered very important to follow, however they may be pushed in some edge play scenes to heighten sexual arousal. Asphyxiation is common within edge play sub-sections of BDSM.
Some types of fear play may take advantage of a persons doubts, such as abandonment (some submissives report being tied up and left alone for hours, sometimes days at once), or humiliation. Others are more physically based. Medical play, knife play, or kidnappings may include a psychological aspect of fear, but it may be the physical activity that causes the emotion.