Photo: Peter Rosa

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Myth: For healthy hair, you should brush vigorously every night to distribute oils.

Fact: Brushing will indeed disperse some oil and sebum along the hair shaft, increasing shine. But don't be too zealous: Brushing also causes friction, which can lead to cuticle damage, breakage, and increased frizziness, says Francesca Fusco, MD, assistant clinical professor of dermatology at the Icahn School of Medicine at Mount Sinai.

Myth: A cold-water rinse closes the cuticle, leaving your hair frizz-free and shiny.

Fact: Water temperature won't make your hair cuticle close or open. But if your strands seem smoother and shinier after an icy rinse, you may not be imagining it. When you use cold water, you're likelier to leave behind more of the oils or silicones from your conditioner, so your hair may appear sleeker and more luminous, says Wilson.

Shirt, Caroline Constas. Earrings, Aurate New York. Ring, Elizabeth and James.