Use Hot Water For A Deep Cleaning:
Using hot water–as hot as is comfortable–will open pores and break up oils near the scalp. The warmer the water, the more oils will break down and be carried away with a rinse. If the hair has extra product or oil on it, hotter water may be the best choice for a thorough cleaning.
Too Much Hot Water Can Be Harmful:
Using hot water on a regular basis is generally not recommended. If too much of the natural oil is stripped away, then the skin of the scalp could become dry. Also, too much heat–whether from hot water, hot curlers or hair dryers–will eventually cause damage to the individual hairs, causing breaks and split ends. This is a greater concern for those with long hair that is not trimmed as often.
The temperature used at most salons for shampooing is lukewarm to warm. For everyday washing–or every other day, as some recommend for preserving natural oils–warm water allows much of the dirt and oils to be carried away, without adding enough heat to dry out the scalp or damage the hair. For extra shine, follow with a cool-water rinse to “lock in” moisture from conditioner and close up hair follicles on the scalp.