Menstrual bikini - Sidsel briefs
Why you'll love this style
Why you'll love this style
WHO IS IT NAMED AFTER?
WHO IS IT NAMED AFTER?
MATERIAL
MATERIAL
WASHING GUIDE
WASHING GUIDE
HOW DOES IT WORK?
HOW DOES IT WORK?Menstrual swimwear, like Flow menstrual panties, is sewn with a built-in pad, consisting of a minimum of 3 technical layers that direct fluid into the pad, absorb the fluid and ensure that you do not bleed or leak through.
👉 You can read much more about how menstrual swimwear works in the guide here.
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Flow's founder
Relaunch of Period Swimwear 2026
"Period swimwear is back! We've spent two years perfecting the fit and materials (we've chosen the best Italian fabrics).
Last summer, I tested the function and fit. I'm not usually a water baby, but of course, the samples I had in my suitcase had to pass their big test.
They passed with flying colours. I felt safe, comfortable - and chic. I'm incredibly excited to see you in the swimwear on the beach, by the pool, in gardens".
- Cathrine
Want to know more about our menstrual swimwear?
Frequently asked questions
Please wear your regular size in your swimwear.
If you are between two sizes, we would suggest the smaller one, as the fabric can stretch when wet.
The absorbency of menstrual swimwear is light to moderate.
If you are bleeding heavily, we suggest that you combine it with a cup or a disk.
Our swimwear is designed with a built-in, absorbent layer that captures and encapsulates menstrual blood. This layer is combined with a waterproof yet breathable membrane that prevents you from bleeding through while swimming or sunbathing.
The textiles are light and quick-drying, ensuring that you can move freely and feel dry shortly after being in the water.
1. If you have bled in your menstrual swimwear, rinse them in cold water until it runs clear.
2. Protect your swimwear in a laundry bag and wash your panties with similar colors at 30-40 degrees.
Tip: You can wash with our Allergy Certified special detergent Bloody Clean .
3. Dry them inside out on a clothesline - and you're good to go again.
👉 Read our full guide on how to take good care of your swimwear here.
Menstrual bikini - Sidsel bikini bottom
Sidsel bikini briefs are a menstrual bikini that combines elegant design with discreet protection. The nostalgic structure of the exclusive Italian fabric gives a timeless look, while the built-in absorbent technology makes it possible to bathe with greater confidence – even when you are on your period.
The bikini bottom is high-waisted and looks and feels like a regular bikini. The only thing you can't see is the sewn-in absorbent panel with three functional layers, which is designed to protect against light to moderate bleeding.
How does a menstrual bikini work?
The Sidsel bikini brief is designed with a discreet absorbent gusset, which is integrated directly into the bikini brief. It helps protect during menstruation without making the bikini feel thicker or heavier than regular swimwear.
The close-fitting construction and three functional layers provide extra security when swimming, bathing or relaxing on the beach.
If you have heavier periods, you can combine the menstrual bikini with a menstrual cup or menstrual disc for extra protection.
Designed for your entire cycle
A menstrual bikini isn't just for the days you bleed.
The Sidsel bikini brief can be worn all month long and works just like a regular bikini when you're not on your period, making it a versatile choice whether you're going on holiday, to the beach, by the pool or at the spa.
The nostalgic wrinkled structure gives an exclusive look, while the lined construction ensures extra support and a flattering fit.
Italian quality with a focus on comfort
Sidsel bikini bottoms are made from an exclusive Italian swimwear fabric with 4-way stretch, which follows the body's movements and provides a comfortable fit. The material dries quickly after a trip in the water and is designed to maintain both shape and comfort season after season.
The lined construction provides extra support, so the bikini bottom stays where it's supposed to be - both when you're swimming and moving around on the beach.
That's why many people choose Sidsel
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Menstrual bikini with discreet three-layer absorbent technology
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Protects against light to moderate menstruation
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Can be used throughout the cycle – even without menstruation
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Looks and feels like a regular bikini
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Nostalgic wrinkled design in exclusive Italian fabric
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4-way stretch for high comfort and good freedom of movement
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Quick-drying material
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Lined for extra support and a secure fit
Match with the rest of our menstrual swimwear
Sidsel menstrual bikini is part of Flow's menstrual swimwear collection and can be matched with our bikini tops for a complete bikini set.
The entire collection is developed with a focus on comfort, function and timeless design, so you can bathe, swim and enjoy the summer – no matter where you are in your cycle.
Frequently asked questions
How does a menstrual bikini work?
Sara Bottom has a discreetly sewn-in absorbent panel with three functional layers. The panel is designed to protect during light to moderate menstruation, while the bikini looks and feels like regular swimwear.
Can I bathe and swim with the menstrual bikini?
Yes. The Sidsel menstrual bikini is designed to be worn both in the water and on land. It allows you to bathe, swim and enjoy the beach with greater confidence during your period.
Can I use the menstrual bikini without menstruation?
Yes. The Sidsel menstrual bikini works exactly like a regular bikini and can be worn all month long – even when you're not menstruating.
What if I'm bleeding heavily?
The Sidsel menstrual bikini is designed for light to moderate periods. If you have heavier bleeding, we recommend combining the bikini with a menstrual cup or menstrual disc for extra protection. Many also choose to change bottoms as needed on longer beach days.
Does the bikini get heavy when it gets wet?
No. The menstrual bikini is made from an exclusive Italian swimwear fabric with 4-way stretch, which dries quickly and is designed to maintain a light and comfortable fit – both in and out of the water.
Can you see the absorbent layer?
No. The absorbent panel is discreetly integrated into the bikini and is not visible from the outside. Sara Bottom is designed to look like a regular bikini.
How do I wash my menstrual bikini?
Rinse the bikini in cold water after use and then wash it according to the washing instructions. Avoid fabric softener as it can affect the absorbent properties. Let the bikini air dry for the best possible care of the materials.
Can I wear the menstrual bikini on the beach for a whole day?
Yes, many do just that. How long you can use it depends on your bleeding. For light to moderate periods, it can often be used for many hours, while for heavier bleeding, you may benefit from combining it with a menstrual cup or disk or bringing an extra pad.
Is the menstrual bikini only for adults?
No. Menstrual swimwear can be a good solution for anyone who menstruates. It gives many people greater freedom to bathe and swim without worrying about their period.
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