Reaction of the body to heat In massage school we are being taught hydrotherapy -- applying cold and heat to specific areas. It says that when applying cold, first the body goes through vasoconstriction, and then later vasodialation. That makes sense -- preserve heat through the former, but if the cold is applied for too long the body still has to keep the cells alive, thus the latter. What doesn't make sense is this passage, in relation to applying **heat** : > Law of Action and Reaction: Initially blood will rise to the surface, applied for too long the blood will recede to the interior causing inner congestion to be greater than before Is that true?

Local warming of a patch of skin will cause vasodilation. However, after prolonged warming there is a 'die away' phenomenon, is which blood vessels slowly constrict back to their normal diameter.

> Johnson JM, Kellogg DL Jr. Local thermal control of the human cutaneous circulation. J Appl Physiol (1985). 2010;109(4):1229–1238. doi:10.1152/japplphysiol.00407.2010
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