I have always heard that rinsing hair in cold water makes it look more shiny and healthy and so I tried it years ago and I am positive it works! That is why I run my hair under water for thirty seconds under cold running water which will help seal the cuticles on the hair shaft. This traps moisture in the hair and creates that gorgeous hair shine like on the commercials. The cold water also constricts the opening of the sebaceous glands to help moderate sebum production on the scalp.
Now, sometimes rinsing with cold water in the shower makes me cringe and I pretty much hate it, but there is a better way. So, if you would rather not rinse in the shower, add cold water to your spray bottle and spray your hair in sections before drying and styling. Another way would be to place your liquid leave-in product in the fridge for 20 minutes while you are showering and spray hair before blow-drying or air drying. And the reward for this cool finish is beautifully shining hair! I have been rinsing with cold water for many years and I just want to share my secret with whoever wants to listen/read.