The chemicals used to color, relax, or straighten hair open up the hair shafts and make them more porous, so they’re more prone to damage.

Maintenance: Wait at least one day after coloring before you shampoo. “The hair shafts need to repair themselves, and washing right after a dye job can remove the color slightly,” says Lavoy. Use a shampoo for color-treated or damaged hair about three times a week and follow with a protein-based conditioner. African-American women should shampoo only about once a week and condition “with a water-soluble conditioning oil,” says salon owner Johnny Lavoy.

Styling: Use a leave-in conditioner fortified with antioxidants and UV filters to protect chemically treated hair. A rich styling cream or hair oil is great for touching up relaxed hair and dry ends. “Stay away from greasy, petroleum-based products, which just coat the hair and seal out moisture,” says stylist Barbara Eisenberg.

Common Misconception: Chemically altering hair is a sure way to destroy it. Only consecutively applied chemical processes, such as bleaching and relaxing, will harm hair shafts beyond repair.

What’s to Love: Relaxed hair is easier to style; colored hair feels thicker.

RS Picks for Chemically-Treated Hair

Pantene Pro-V Restoratives Breakage Defense Shampoo ($5 at drugstores) helps fill in the weak parts of each strand, making hair more resilient.

Redken Smooth Down Detangling Cream Leave-In Smoother ($15, www.redken.com for salons) conditions with macadamia oil to tame frizz.

Carol’s Daughter Tui Hair Oil ($17.50, www.carolsdaughter.com) contains a botanical oil to add moisture and sheen to African-American hair.