The muscles located in the hair follicles contract resulting in goosebumps. As a result, it raises the hairs and leads to a goose bump or rough skin surface. Goosebumps can be caused by a variety of factors, including:

Cold: During coldness, our bodies attempt to retain warmth; blood vessels are constricted while hairs go stiff and erect. This forms a blanket layer that may assist in trapping some body warmth.

Strong emotions: The other cause of goosebumps is strong emotions such as fear, excitement, awe, and sexual arousal. The pilomotor reflex is initiated when our bodies secrete hormones due to experiencing these kinds of emotions. Pilomotor or primitive reflex is an innate response that developed possibly as a mechanism for survival in the face of danger. Standing our hair up may make us look bigger and therefore frightening to possible enemies.

Music: We can also experience goosebumps while listening to something that moves us such as a particular song. Music has been found to be capable of releasing an important neurotransmitter known as dopamine which has been attributed to be responsible for feelings of pleasure and reward. The pilomotor reflex is another process that can be activated by dopamine release.  

• Goosebumps are usually linked with unpleasant feelings like fear but you may experience them in case of happiness or excitement. The presence of the pilomotor reflex implies that it is a highly intricate reaction and its entire mechanism remains unclear.  
• Some individuals are more susceptible to getting goosebumps than others. This could also be because of a genetic component and disparities in how the body’s nervous system reacts to particular stimulants.  
• The reaction of goosebumps is a benign physiological phenomenon. Nevertheless, if these goosebumps become too extreme or occur with other symptoms like fever/chills make sure you visit a doctor.