This podcast details goosebumps, or piloerections, as an involuntary reaction of the sympathetic nervous system, part of the fight-or-flight response, where tiny arrector pili muscles at hair follicles contract, making hairs stand on end.

Common triggers include cold weather, intense emotions such as fear, shock, anger, or excitement, as well as intimacy, sexual arousal, and frisson from external stimuli like music, movies, or ASMR.

Evolutionarily, goosebumps helped furry animals conserve heat by trapping an insulating layer of air and made them appear larger to deter predators. A recent study revealed a deeper purpose: the nerves and muscles causing goosebumps also stimulate hair follicle stem cells and new hair growth, acting as a long-term response to cold. This involves sympathetic nerves directly interacting with stem cells and releasing neurotransmitters like norepinephrine.

Psychologically, experiences like music can trigger goosebumps when the emotional brain perceives an unexpected stimulus as a threat, followed by the thinking brain's cognitive reappraisal, which releases dopamine and creates a pleasurable sensation known as frisson or a "skin orgasm".

While generally harmless, persistent goosebumps without a clear cause can sometimes be a symptom of underlying conditions such as keratosis pilaris, anxiety, withdrawal from substances, certain types of seizures (e.g., left temporal lobe epilepsy), or autonomic dysreflexia.