PRO: Seals the Moisture in Your Hair
Just the opposite of hot water, cold water closes the pores and prevents dirt from entering and accumulating on the scalp. Not only does it close the pores, it also closes the hair cuticle, sealing in moisture from the conditioner that you applied to your hair. Whereas hot water can remove the moisture from your hair, cold water retains the moisture and the natural sebum that’s so beneficial. Don’t forget, more moisture means less frizz. Cold water retains your hair’s moisture, leaving your hair less prone to frizz.
PRO: Increases Shine
Sometimes stylists like to finish blow drying with a blast of cold air because it leaves the hair shiny. The same concept can be applied to a cold water rinse. Cold water is known to smooth the hair by closing the scales of your hair cuticle, which in turn prevents frizz and adds luster to your locks.
CON: Flattens Hair
Because cold water leaves the hair smooth, it can also flatten your hair if you have a naturally thin texture. If your hair lacks in volume, or if you live in a particularly arid environment, rinsing your hair with cold water might result in flat hair and curls with no bounce.