Material
Swimwear
Nylon or polyester with elastane. It barely stains, and the rules are all about protecting the stretch from chlorine, heat and machines.
- SurfaceNon porous
- WashingHand
- Colour run riskMedium
- Reviewed7 September 2026
What swimwear can and cannot take
- Heat Avoid
- Water and soaking Tolerates it
- Acids, including vinegar Use with care
- Strong alkalis Use with care
- Solvents Avoid
- Chlorine bleach Avoid
- Abrasives Use with care
Always test on a hidden area first and let it dry before you treat the visible mark.
General rules for swimwear
Rinse it in cold water by hand, immediately, and that is most of the job. Swimwear is nylon or polyester with elastane, none of which absorbs, so a milk mark has very little to hold onto.
Everything else is a list of things not to do. No machine, no dryer, no iron, no chlorine bleach, and no leaving it rolled up wet in a bag.
Dry it flat in the shade. Direct sun degrades the elastane and fades the print.
Check the label
UK swimwear retailers are unusually strict about this and the reasons are good: hand wash in cold water only, never machine wash even once, never tumble dry, never iron because high temperatures make the fabric disintegrate, and never chlorine bleach because chlorine resistant does not mean chlorine proof.
Stains on swimwear
- Baby sick Rinse it by hand in cold water immediately, then hand wash with a little mild detergent and rinse again. Swim...
- Blood Blot first, then use cold water and a tiny amount of compatible detergent. Work from the edge, rinse or blot...
- Body oil Dry blot swimwear, then wash only if the care label permits it using diluted delicate detergent. Do not apply...
- Breast milk Dry-blot first. Use this route only on an unstructured item whose whole label expressly permits hand washing....
- Bronzer Lift loose bronzer from swimwear before it is rubbed in. Blot cream bronzer, follow the material or care labe...
- Coffee Blot without rubbing. Support the fabric and check the care label before adding water. Use a brief fibre-appr...
- Concealer Lift the concealer, flush Swimwear from the back with cool water, pre-treat the oily residue with one drop of...
- Deodorant Rub a fresh white deodorant mark off swimwear while it is dry. For residue that remains, follow the care labe...
- Hair dye Blot Swimwear, flush cool water through the back, pretreat with liquid detergent, wash to the care label and...
- Lipstick Lift lipstick from Swimwear, work from the reverse with a drop of washing-up liquid, rinse cool, wash to the...
- Nail polish Lift accessible free polish without rubbing and keep the item dry. The fibre, finish or construction makes a...
- Period blood Lift any tissue with a spoon edge, then blot. Use cold water and a tiny amount of compatible detergent for th...
- Pet urine Blot until nearly dry, then use only the cool-water quantity swimwear can tolerate. Use a labelled pet urine...
- Sweat Rinse fresh sweat from the back of Swimwear with cool water, pretreat retained residue, wash to the care labe...
- Tomato sauce Lift tomato sauce from Swimwear, flush from the reverse with cool water, pretreat the remaining film, wash to...
Swimwear is a small amount of fabric engineered to stretch a long way and to survive chlorine, and the elastane in it is the part that ages.
It hardly stains
The fibres are smooth and non absorbent, and the fabric is usually a bold print or a dark colour. A milk mark rinsed out in cold water within a few minutes generally leaves nothing at all.
The rules protect the elastane
A retailer's instruction not to machine wash a swimsuit even once is about the agitation and the spin cycle, not about the water. The instruction not to iron it is because the fabric disintegrates rather than merely creasing.
Chlorine resistant is not chlorine proof
Chlorine resistant fabrics simply last longer in a pool. Household chlorine bleach is far more concentrated and destroys the elastane outright.
The 24 hour rule
Retailers suggest alternating swimsuits and giving elastane a day to recover between wears. That is also good advice after washing one.
Sources
What we checked and when. Where a manufacturer instruction disagrees with anything here, follow the manufacturer.
-
How to wash swimwear, Simply Swim
retailer
UK swimwear retailer guidance to rinse swimwear by hand in cold water after every use because water alone does not remove chlorine or salt, never to use chlorine bleach because chlorine resistant does not mean chlorine proof, never to machine wash or tumble dry swimwear even once, never to iron it because high temperatures make the fabric disintegrate, and to air dry it in the shade allowing 24 hours between wears for the elastane to recover.
Checked 7 September 2026
-
How to clean polyester and synthetics, Woolite
manufacturer
Detergent manufacturer guidance that polyester is washed, dried and ironed at low to medium heat only because excessive heat can melt the fibres, that air drying is preferred to machine drying, that nylon is washed in cool water on a gentle cycle because repeated machine washing causes discolouration and loss of shape, and that acrylic knits are laid flat or dried at low temperature to keep their shape.
Checked 7 September 2026
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How to remove baby formula stains, Purex Stain Lab
manufacturer
Manufacturer guidance identifying breast milk, formula and baby spit-up as protein stains, explaining the role of enzymes, and warning that the mark should be checked before any drying heat because heat sets what remains.
Checked 7 September 2026