What is period underwear? This is how they work and this is how you choose
Maybe you have considered trying period underwear.
Maybe you are curious if they really work. Or maybe you're wondering if they can replace pads or tampons - and if they can stay tight at all.
If you have questions, you are far from alone.
period underwear has become a popular alternative to traditional menstrual products. For some, they are the only solution they use during menstruation. For others, they work best as extra protection on the hottest days or at night.
There is no one-size-fits-all solution.
But if you understand how period underwear works, it also becomes much easier to choose the model that suits your body and yours period.
This guide was written by Cathrine Widunok Wichmand,
journalist + founder of flow
What is period underwear?
period underwear looks and feels like ordinary panties.
The difference is on the inside: Several functional layers are sewn into the crotch, which together can absorb menstrual blood and help keep the skin dry.
This means that many can use period underwear alone in light to moderate period, while others choose to combine them with a tampon, menstrual cup or menstrual disc on the heaviest days.
They are available today in many different models – from high-waisted briefs and shorts to g-strings and teenage models.
Therefore, it is not only about absorption, but also about comfort, fit and what suits your everyday life best.
See our selection of period underwear here
How does it work period underwear?
Although they look like regular underwear, are period underwear developed with several layers, each with their own function.
1) The top layer directs the liquid away from the skin, so the panty feels drier.
2) The absorbent layer collects the menstrual blood and keeps it inside the material.
3) There is a liquid-tight membrane on the outside, which helps protect against soaking.
Exactly how the layers are constructed varies from brand to brand. Therefore, both comfort, breathability and absorption can also vary.
Just as important as the materials is the fit: One period underwear, which closes tightly around the legs and fits well on the body, provides the best protection against leakage.
What are the benefits of period underwear?
There are many reasons why more people choose period underwear.
For some, it's all about comfort. For others about security. And for many, it's the combination.
Some of the benefits include:
- They feel like regular panties.
- They can be used again and again.
- Many experience greater security against leakage.
- They can be used alone or together with other menstrual products.
- They are suitable both during the day and at night.
This does not mean that period underwear is the right solution for everyone. But for many, they quickly become a natural part of the menstrual routine. But there will always be a few bleeds at the start, where it's a bit of trial and error - both to match your bleeding amount with the right absorption but also to find your fit and size.
The size is important for the panty to actually work - if it is too big and therefore loose, you will typically bleed on the side.
You can read more about the pros and cons in our article What are the benefits of period underwear?
Which absorption should you choose?
The best choice depends on you flow.
Most people experience that menstruation changes throughout the cycle. The first days can be intense, while the last days are often much lighter.
Therefore, many choose to have more than one type period underwear.
Our panties with low absorption are also super good as a replacement for panty liners for discharge and spotting.
If you have very heavy periods, it can give extra security to combine period underwear with a tampon, menstrual cup or menstrual disc.
Read Powerful period – when do you bleed too much?
How many period underwear do you need?
We get that question often. There is no one right answer.
It depends, among other things, on:
- how heavily you bleed
- how often you wash clothes (if you have access to your own machine, it's a little easier)
- if you use period underwear the whole period or only some of the days.
Too many are 3-5 pairs a good place to start. Then you have the opportunity to wash between uses without running out.
If you are using period underwear throughout the period, it can be nice to have several pairs. Here we recommend 10 pairs for a truly comfortable experience.
That's why we always have bundles - you can save up to 20% by buying 5 pairs or more.
How to use period underwear
It usually only takes a little getting used to. You simply put them on as you would ordinary panties.
How long they can be used at a time depends on:
- your flow
- absorption of the model
- what you yourself feel comfortable with.
If you try period underwear for the first time, it may be nice to test them at home on a day when you have easy access to change.
Then you quickly get to know both fit and absorption.
How to wash period underwear
If you take good care of yours period underwear, they can last for many years.
A simple washing routine is usually enough.
We recommend:
- Rinse the panties in cold water after use
- Wash them according to the washing instructions with a mild detergent, which we highly recommend Bloody Clean, which we have developed specifically for period underwear - it also effectively removes any odor
- Avoid fabric softener as it can affect absorbency
- Let them air dry
Read the guide How to wash period underwear
Are period underwear free of PFAS?
Many have become more aware of which materials menstrual products contain.
That also applies period underwear. Therefore, it may be a good idea to investigate which materials the manufacturer uses and whether the company is open about the content of its products.
At flow we use neither PFAS nor biocides such as nanosilver in ours period underwear. The materials are also OEKO-TEX® STANDARD 100 certified.
Read more about PFAS in menstrual products – what does the research say?
Who is period underwear particularly good at?
period underwear can be used by most people.
They are, among other things, popular with:
- people who want an alternative to pads and tampons
- teenagers who have just had period
- people with special requirements for tactility and sensitivity
- people with mild incontinence
- women after childbirth, when the heaviest bleeding is over
- people who want extra security against leakage
SEE our selection: period underwear for teenagers
How to choose the right ones period underwear
The most important thing is not to find the "best-in-tests" period underwear. The most important thing is to find the ones that suit you.
Consider, among other things:
- How powerful is yours flow?
- Should they be used during the day, at night or both?
- Will you use them alone or with another menstrual product?
- What fit do you feel most comfortable in?
For many, it makes sense to start with a few different models and find out what works best in practice.
For period are not the same.
Neither from person to person – nor from day to day.
