Fear is an emotion that typically occurs when one perceives a threat to personal well-being, can prompt action against the threat. A common emotion that is experienced by most individuals at some point or another, fear is considered to be a normal, natural part of life.  However, fear can lead people to experience a wide array of physical and mental changes, and irrational or intense fear may interfere with a person’s happiness, sense of security, and ability to function effectively.

When fear is persistent or has a negative impact on daily function, a therapist or other mental health professional may be able to help an individual address this challenge.

Without fear, an individual's chances of day-to-day survival would likely diminish. Thus, fear can be healthy, because it helps people keep away from dangerous or harmful situations. Fear can often affect physiology when a threat is perceived. One's heart rate, breathing, brain activity, muscle tone, and startle response are all likely to experience temporary changes. Typically, fear also elicits a "fight or flight" response, which is a biochemical reaction to stress. 

All people are likely to experience fear of some sort. Humans and animals typically possess innate fearful reactions to some stimuli (such as unexpected or loud noises), and some of these stimuli may differ from one person to the next, although some fears may occur frequently in the general population. For example, a great number of people report a fear of death. New fears are often learned when fear-inducing stimuli are paired with objects