Cold chill up your spine?

Question

Hey docs, what causes that chill to go up my spine when the weather is nipping? What is that sensation chemically?

Answer 1

Spasmodic muscular contractions are one way the body heats itself, so it's a natural reaction to cold or especially cold winds
which are more 'chilling'.
Think about the chills (muscle contractions) you have with the flu. In that situation the body is heating up - causing an increase in body temperature which we call a fever.
It's not so much chemical as it is a neuromuscular reflex. (Though neuromuscular reflexes are mediated by chemicals - esp, acetylcholine)
MD answer

Answer 2

I don't know the medical explanation, but the old wives' tale (superstition) says it means someone had walked right over the very spot where your dead, cold body will eventually be buried years from now. If you live a long, fruitfull life, (hopefully), then you should die of old age, maybe in your early 70s or beyond.