Chills, often referred to as shivers or goosebumps, are physical reactions that occur in response to fear or anxiety. This sensation is caused by the body's fight-or-flight response, which releases adrenaline and triggers the contraction of tiny muscles at the base of hair follicles. This reaction can make a person feel cold or cause a tingling sensation along the skin. When experiencing chills due to fear, individuals may also exhibit other symptoms such as increased heart rate and heightened alertness. This response is a natural survival mechanism, preparing the body to react to potential threats in the environment, similar to the way animals respond to danger in the wild.