Make sure to wash your swimsuit after each and every wear—even if you don’t go in the water. “Sunscreens contain ingredients that can be damaging to the fabric and can lead to the eventual breakdown of the material,” says Marysia Reeves, designer of Marysia Swim. To top it off, some SPFs are more detrimental than others, warns Lindsey J. Boyd, co-founder of the all-natural detergent line, The Laundress. Mineral-based lotions and oil formulations can cause yellowing or gradual stains over time if swimsuits are not washed properly. The spandex fibers in swimwear that provide the stretch are the most susceptible to breakage and discoloration from chlorine and body soil. The best thing you can do for your swimsuit is to rinse it out in cool water as soon as you take it off. Even better, fill a sink with cool water and let the suit soak for about 30 minutes to remove most chemicals and body soil that can damage the fabric. Get a head start by filling a leak-proof plastic bag or small container with clean water and add your swimsuit to soak on the trip home from the pool or beach.

How to Wash a Swimsuit by Hand

Washing a swimsuit by hand is best because hand-washing is gentler and helps prevent stretching. Fill a sink with lukewarm water and add a gentle detergent formulated for activewear like Hex Performance Laundry Detergent. One teaspoon of any detergent is enough to clean a single swimsuit. In a pinch, Boyd also swears by adding a splash of white vinegar, known for its deodorizing and antibacterial properties, in lieu of detergent. Turn the swimsuit inside-out. Use a dab of the laundry detergent on a soft-bristled nylon brush (an old toothbrush works great) to gently scrub necklines and areas that may have sunscreen stains. Swish the suit through the sudsy water while you gently squeeze the fabric for several minutes. Empty the sudsy water and refill the sink with cool, clean water to rinse the swimsuit. Gently squeeze out the water—no wringing! Roll the swimsuit in a terrycloth towel to absorb excess water or simply hang it to air-dry in a spot with good air circulation, away from direct sunlight, which can cause colors to fade. Add a circulating fan to speed drying. Skip the dryer because high temperatures can permanently damage the fabric.

How to Wash a Swimsuit in the Washing Machine

If you are using a washing machine, it’s a good idea to wash the swimsuit with similar types of synthetic fabrics. (Wash beach towels in a separate load). Turn the swimsuit inside-out, and treat the appropriate areas for sunscreen stains with a dab of gentle detergent. Place the suit in a mesh laundry bag to prevent snags and stretching. Set the washer to the gentle cycle and use cold water and a gentle detergent. When the cycle is finished, remove the swimsuit from the bag and hang it to air-dry.

Avoid These Don’ts:

Don’t soak a swimsuit overnight. This can loosen fibers.Don’t let a swimsuit dry directly in the sun. This may cause fading.Don’t put a swimsuit in the dryer. The heat weakens the elasticity of the spandex. This is the same reason why you shouldn’t wear your favorite bikini in a hot tub.Don’t hang a swimsuit on a metal rod to dry. Hanging can alter the shape of the garment, while the metal rod could leave a rust mark that’s impossible to get out.Don’t sit on rough surfaces while wearing a swimsuit. The concrete beside the pool or wood from the lounge chairs may snag the swimsuit material. Always lay down a towel before you sit.