The Right Way To Care For Your Hair #1

When to switch shampoos, plus how pollution really affects your skin.

By Elizabeth Koppelman

Q: I've heard that hair "gets used" to shampoo, so you should switch brands every few months. True?

A: Not exactly. "Shampoo ingredients don't accumulate in your hair, so there's no reason to make a preventive change," says New York dermatologist Francesca Fusco, M.D. But swapping shampoos can be beneficial if you habitually use styling products (they can build up on hair, making it dull) or live in an area with hard water (which contains high concentrations of radiance-busting minerals). Alternating your regular shampoo with a clarifying one once every few weeks, however, can deep-clean hair and remove buildup. Clarifying best bets: Herbal Essences Drama Clean ($3) with shine-enhancing berry-tea extracts and Dove Beautifully Clear Shampoo ($4; both at drugstores), which nourishes locks with glycerin.