DIAGNOSIS: Green swimmer's hair.
CAUSE: Proteins in your hair and copper found in pool water create a chemical reaction.
SELF-HELP: Wash hair with a clarifying shampoo like Pureology Perfect 4 Platinum Shampoo, which is void of color-altering sulfates and sodium chloride immediately after a dip to get rid of mineral deposits. In a pinch, rinsing hair with equal parts white vinegar and water also does the trick, says Teca Lewellyn, Procter & Gamble Beauty scientist.
PRO RX: For really stubborn stains, opt for a salon formula that can chemically lift discoloration with bleach, Lewellyn advises. "Bleaching can cause dryness, so ask your colorist to use fast-acting formulas that are less likely to fry your hair." Try: Wella Professionals Blondor Multi Blonde Powder.
PREVENTION: Bleached hair is more porous, which causes it to soak up extra copper and chlorine in the pool, explains Lewellyn. If sporting a silicone swim cap isn't your style, she recommends rinsing hair with fresh water and coating strands with a leave-in conditioner (to minimize the absorption of chemicals by cuticles) before jumping in.
DIAGNOSIS: Fried ends.
CAUSES: Too much styling or bleaching.
SELF-HELP: "A telltale sign you've done major damage: short bang-like pieces that aren't part of your haircut," explains celebrity colorist Michael Canalé. Intense breakage from overbleaching requires heavy-duty therapy like Living Proof Restore Recovery Regimen, a monthlong repair system with patented moisture-binding molecules. Or try a DIY hot-oil treatment: Mix 4 tablespoons of olive oil with 1 tablespoon each of coconut oil and protein-rich conditioner; comb through; cover hair with a plastic cap for deeper penetration; leave on for an hour (or even better, overnight); then rinse with warm water.
PRO RX: Bottle blondes are subjected to higher levels of peroxide, says Canalé. For super-stressed strands, he suggests an intensive salon prescription like the Shu Uemura Art of Hair Silk Bloom Restorative Treatment that fortifies frail hair with a potent cocktail of vitamin E, ceramides, and argan oil.
PREVENTION: "If you can get away with it, skip the double process and just highlight your hair to avoid excess damage," Canalé advises.
CAUSE: Mineral deposits in hard water.
SELF-HELP: "A violet color-correcting shampoo with cool tones helps counteract any yellowness," says Dhaniel Doud, manager of Redken Education. Just make sure you distribute it evenly through wet hair and leave it on for five minutes max, he warns. "The goal is to create a super-sheer lavender veil on hair that masks yolky hues not to sport purple streaks."
PRO RX: Ask your colorist for a few face-framing baby-blonde highlights (which instantly brighten), followed by a professional-grade, ammonia-free toner to diffuse any leftover brassiness.
PREVENTION: Invest in a good shower filter that blasts calcium deposits, and wash hair every other day to prevent color from fading, says Tammy Sherman, creative director at the Frédéric Fekkai Salon at NYC's The Mark Hotel. In between shampoos, rinse with lukewarm water and use an ultra-hydrating conditioner like Fekkai Advanced PrX Reparative Conditioner.
MC RECOMMENDS: Clairol Pro Shimmer Lights Blonde & Silver Shampoo, $9 (top center); Paul Mitchell Forever Blonde Dramatic Repair, $18; Aveeno Nourish+Strengthen Conditioner, $7; Living Proof Restore Recovery Regimen, $38 for five ampoules.