A Complete Guide to Period Underwear
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A Complete Guide to Period Underwear

by Aisle Team
A Complete Guide to Period Underwear

Period underwear, period pants, period panties — or period undies as we like to call them here at Aisle - whatever you want to call them, they are having a bit of a moment right now. And, let’s be honest what’s not to like? Comfortable, eco-friendly, and easy-to-use; period underwear really does have it all!

Maybe you’ve never tried period underwear before. Maybe you think they’re a myth. You might even think they’re gross (btw they’re not). We’re here to give you the low-down so you can figure out whether they’re the right fit for you. This period-packed guide has everything you need to know about period pants — so get absorbing!

The history of reusable period products

Before we begin to talk about period undies, we have to talk about reusables more generally. By that, we mean period products that can be reused again and again.

Reusable products are the OG period products. From lint, and buffalo skin to fabric rags (“on the rag” get it!?) people were using all kinds of reusable items before disposable pads and tampons came along. Even the menstrual cup was a pre-disposable invention patented in 1867. 

Period underwear does stand at the feet of the many reusable innovations before them and you can think of us as the OG of modern reusables. Back in 1993 (when we were named Lunapads) we were one of the first companies to create cloth pads commercially. Over ten years later, we’ve taken that first-hand knowledge into creating period underwear. With over a decade of testing and innovation in sustainable period products you know we’re one to trust.

The Basics

What is period underwear?

As we’ve just said, period undies are pretty awesome. But what are period underwear? Put simply, period undies are underwear that are specifically designed to absorb menstrual blood. It’s a complete replacement for pads, tampons, and cups. You just pull up and period.

The benefits are endless; reduced monthly waste (the planet says thanks), more comfort, breathable (goodbye irritation), and more convenience because you don’t need to buy new products every month (hello $$$). Period underwear has it all! 

Do period underwear really work?

Are period underwear worth it? TLDR; yes thanks to modern technology! 

But, you’re probably wondering what that tech is and how period underwear works. The magic comes from the triple-layered fabric. Layer one is our special moisture-wicking meaning fabric that draws fluid away from your body; it’s followed by a superabsorbent core that absorbs your period blood. This is all surrounded by our special leak-proof membrane that catches any of those stray blood drops. 

Aisle products are built for comfort and performance — that means our period undies too! Don’t believe us? All our products are lab-tested and verified by third-party data to meet our high standards for absorbency and leak protection. So we’re period-proven.

How much does it cost to use period underwear?

Let’s be real here, transitioning to period underwear can feel like a big upfront investment. Period underwear can range anywhere from $15 to $50 each — and since most people need around 3 to 5 pairs per cycle — that can rack up quite a big bill.

But remember: every $ you spend now is working towards a $750 saving over five years! Better for your purse and the planet. 

We get that the upfront cost might be a little spendy, so we recommend swapping a couple of days for undies to start. Then, once you figure out what works for you, you can add more products to your roster later. It’s a big transition — no need to rush it. 

Oh and did we mention that we’ve got a special discount for packs of 3 or 5 undies?  We’ve got your back (and front).

How to use and care for period underwear

​​There’s a bit of a learning curve when it comes to reusables, but once you know how it’s as easy as — well wearing underwear.

The first thing you need to know is that our period underwear needs to be washed after 12 hours of use, or when the undies are full.

A couple of other tips to extend the lifespan of your undies: 

  • Avoid bleach or fabric softener — they’re not best friends with our products and can decrease their performance and lifespan. 
  • Don’t leave your pads soaking in water — this can lead to bacterial growth and mold (ew!). 
  • Avoid frequent use of bleach products — yes they remove blood stains but they’re also harsh on natural fibers. Try our Stain Eraser instead.
  • If you’re out and about, living your best life, you can carry a bag with you — wet/dry bags are great for this — to hold the period underwear ready for rinsing and washing when you get back home!

How do I wash period underwear?

Right now you’re ready for the main event. Washing your undies. It’s really simple: once you’re done with them, rinse them out in cool water and then toss them in the washing machine and dryer with your regular laundry. As with any garment, wash them with like colors.

Now if you want to get technical, here are some top tips: 

  • Rinse the gusset and boosters in cold running water until they run clear before adding them to your laundry. 
  • Hang to dry where possible — it saves energy and prolongs the life of your undies! Otherwise, machine dry on low.
  • If you’re a hand washer — only use a very small amount of a detergent specifically formulated for washing clothes and be sure to rinse well — don't use concentrated soaps or other hand and dish soaps, as these can leave behind residue that will reduce the effectiveness of your undies.

Oh and if you’re only going to be doing laundry once a week, it’s ok to rinse out your pads/undies and leave them somewhere with good airflow until laundry day. See, we told you it was simple!

How many pairs of period underwear do I need?

Everybody is different and you know your flow best. How many pairs you’ll need depends on the heaviness of your flow and the absorbency you choose. As a general guide, we recommend a pair for each day you bleed. That said, periods are unpredictable so you may want to purchase some extras that you can keep on hand, just in case you’re not feeling that big pile of washing! 

As an example, our BOOST undies hold 4 tampons worth of fluid, but we’ve devised a clever little removable Booster that you can add at any time to give you an extra 4 tampons worth. You can even purchase additional Boosters on their own so you can swap them throughout the day without having to change your actual undies. We’re just out here making periods simple.

How do you know when period underwear is full?

As we’ve said, starting with reusables takes a little bit of trial and error. As your flow is unique to you and can vary across your cycle, you’ll start to get to know how your undies deal with each day of your bleed.

That being said, there are some signs to look out for:

  • Is there blood at the seams of your undies? 

  • Does the gusset (the part closest to your body) feel heavy? 

  • Does the gusset feel heavy or stiff compared to when it was freshly washed? 

  • Is there blood on the gusset that hasn’t been absorbed?

If you notice any of the above it’s probably time to change. So give those undies a rinse and pull out your next pair. 

Do period underwear smell?

Contrary to popular belief period blood doesn’t actually smell! As with other blood, it has a slight metallic smell but only has a strong odor once it has mixed with air. This smell is the same whatever product you’re using — pad, tampon, cup, and even period underwear. 

Here at Aisle, we’re using innovative materials like Tencel™ which makes our undies less susceptible to odor-causing bacterial growth. So, if you take proper care of your underwear (as we’ve told you how), there’s no reason your underwear should smell.

Can I sleep with period underwear?

No one wants to be dreaming about period leaks. Nightmare! That’s why you can be sure to sleep tight (and comfortable) in our period underwear.

Period underwear can be worn overnight for up to 12 hours so doesn’t need to be changed in the middle of the night. And thanks to its cozy, breathable, and soft design with tons of coverage you’re pretty much covered for a sound sleep.

Period underwear for swimming

Since our undies are made with super-absorbent fabrics, we don't recommend wearing them while swimming. There are lots of fantastic brands out there that offer period swimwear that can be worn in water.

What’s the big deal? 

What about the products I use now?

Period underwear absorbs more, saves you money, and does all that without harming the planet.  So if you’re a comfort-seeking, eco-conscious individual these might be the best choice for your body, your values, your lifestyle, and the planet.

Since switching to reusables can come with some learning (and a price tag), let’s break down the pros and cons of period undies: 

Things to consider:

An uncomfortable truth about most period underwear is that you’re getting up close and personal with your period blood. Ok, not menstrual cup close, but you will have to rinse out your undies and see your period blood.

There’s also the fact that you are sitting in your period blood all day (just like a pad). It won’t feel like it and you definitely won’t notice thanks to the power of absorbency fabrics.

If your period undies are full you will need to change them — which can be a bit of a pain in a public restroom! And then you need to carry those undies around until you’re ready to wash them at home. Annoying but if you come prepared with a wet-dry bag and an extra pair, you’re good to go. 

Things to love: 

Every dollar you invest in undies now is working towards a $750 saving over five years! 

They’re one of the most simple period products to use. All you have to do is pull up your undies and get on with your day (until it comes to wash time). 

Period undies are so comfy and breathable — you can forget about irritation and chafing.

Did we mention they’re fantastic for the environment? Each year, over 20 billion pads, tampons, and applicators enter landfills and waterways in North America. Many of these products take over 500 years to biodegrade. Switching to Aisle pads and underwear reduces waste by 99% and C02 emissions by 95%. 

Period undies are pretty damn good-looking. I mean have you seen our Retro Brief? They’re super cute. 

Here are 100 other reasons people just like you love period undies, so you don’t have to take our word for it.

Do you bleed less with period underwear?

I know we said period undies were magic, but sadly they’re not that magical. Period underwear is just like any other product so doesn’t have an impact on how much you bleed, your period symptoms or increased period cramps or blood clots. 

Recently, there have been lots of news articles discussing the use of PFAs in period underwear and the impact this can have on the body and your period. And we’ll delve into that in the next section.

Are period underwear safe?

There’s been a lot of concern recently about PFAS (polyfluoroalkyl substances) and period underwear, so we’re here to set the record straight. 

What are PFAs?

To put it simply: PFAs are a group of chemically manufactured compounds made up of carbon and fluorine. The carbon/fluorine mix is what allows materials made with PFAs to be non-stick as well as water and stain-resistant.

Often referred to as “forever chemicals” because they do not break down in the environment, PFAS can be found in food packaging and apparel. These chemicals are thought to be harmful to human health and the environment because they remain in our bodies and the environment for decades afterward. 

Are there PFAs in my period underwear?

A recent study showed which period underwear has PFAs. Only 6 brands moisture-wicking period underwear brands out of 14 had no detectable levels of PFAs. We are proud to say that Aisle is one of those brands! You can see all the other brands that were tested here

We have had our period underwear third-party tested for PFAS and are proud to say we have no detectable levels of PFAs in our period undies. All our fabrics come with STANDARD 100 by OEKO-TEX® certification and are tested for numerous harmful substances by independent agencies using global standards — something we’ve been doing for decades.

Are PFAs in period underwear harmful?

There is growing evidence that exposure to PFAs can harm individuals’ health, including liver damage, decreased fertility, hormone disruption, and cancer.

Unfortunately due to the decades' lack of research into reproductive health and chemical disruptors like PFAs, we don’t know all the risks right now. Researchers are currently concerned about PFAS and skin contact, especially around the area where period pants are used due to the impact this could have on a person’s reproductive health.

How do I know if PFAs are in my period underwear? 

It’s important to know that nothing can be proven to be PFA-free. So be wary of any brand that makes statements like this. Due to the staying-power of PFAs most everyday items — even if a brand has tried really hard — will have some trace of PFAs in their products.

The best things to look for are: 

  • Whether the period underwear has been independently tested
  • If the brand is open about the amount of PFAs in the product 
  • If the brand provides certification or proof of the PFA claims they are making.

Does all moisture-wicking clothing have PFAS?

PFAs are found more in clothing that is stain-resistant and water-repellant. So a lot of moisture-wicking fabrics — materials that are made to remove moisture from your clothing — contain PFAs. 

However, notice we didn’t say all moisture—wicking fabrics. At Aisle, we have developed Truetex™ a moisture—wicking fabric that absorbs in the same way as other wicking fabrics but without the need for added chemical finishes. Our Truetex™ is Oeko-Tex Standard 100 Certified, which means no harmful chemicals are used in manufacturing.

What if period underwear isn’t for me?  

We believe that everyone has a right to a product that is both good for them and the planet. If that product isn’t period underwear for you, don’t worry there’s plenty more of Aisle. 

So let’s show you what we’re made of, and what kind of products you might use, depending on your flow.

Washable Liners 

Our liners are just like a normal liners but reusable and good-looking. Like our undies, they have ultra-thin leak protection with a patented, high-performance cotton top layer, so they’re perfect for your lightest days or to have with you just in case. And they come in two lengths!

How to use:

Place the liner in your underwear and use the poppers on the wings to secure the liner in place. Depending on your flow the liner can last all day. Bear in mind that we created our thinner liner for light days, spotting, or discharge.

Once you’re finished with the liner rinse in cool water, then wash and dry with your regular laundry. Hang to dry where possible — it saves energy and prolongs the life of your products.

Best for:

  • Light Flow
  • Back up for a cup or tampon
  • In case of emergencies!

Things to consider:

You’ll need to pair liners with some other form of protection on your heavy flow days! They’re super thin, but that also means that they’re not as absorbent as our other products. 

These are great for small bladder leaks as well as spotting.

Menstrual Cup

The menstrual cup is a powerhouse, and if you were looking for a product to carry you through your entire period, this would be it! The Aisle cup comes in two sizes, holds up to 30ml of fluid, and can be worn for up to 12 hours so you can sleep, swim, stretch, and slay all day.

How to use:

Make sure you’ve washed your hands, and are feeling calm (especially if it’s your first try). Hold the cup by the stem, and fold it in half to form a U shape. Get into a comfy position — legs apart squatting or sitting is usually best — and insert the cup into the vagina. You want the stem to be half an inch in and no more. We’ve got more tips here.

Once you’re ready to take the cup out, once again wash your hands and get yourself into a comfy position. Insert your thumb and index finger into the vagina, and pinch the base. (Don’t pull on the stem like a tampon string — it’s just there to help you find the cup.) Once you’ve pinched the base you’ll remove the seal and you can pull the cup out and empty its contents in the toilet. Wash thoroughly and remember to boil at the end of every period! We’ve got more tips here.

Best for:

  • Moderate to Heavy Flow
  • Physical activities (think swimming, hiking, etc)
  • Overnight 

Things to consider:

There’s a bit of a learning curve associated with inserting and removing the cup without making a mess, but there are a lot of great tutorials out there that will help you with that! It’s best to practice insertion/removal around the house so that you feel confident and comfortable with the whole affair before attempting it out in the wild!

Cups are meant to form a seal that prevents leaks, but if you’re worried about leakage of any kind, wearing a liner or period undies as a backup is a great option!

If you’ve got a tilted uterus, a cup might not sit right. You’re not meant to notice the cup when it’s inserted properly, so if it’s causing you pain or discomfort of any kind, you should consider contacting your OB/GYN or trying a different style of cup or menstrual product.

You can totally wear a cup on lighter flow days as well! It's non-absorbent, you won’t be taking any of your vagina’s natural fluid, so you can pop it in even when your period is light. 

Reusable Pads

Our pads are leakproof from edge to edge and we’ve invented a clever layer that moves fluid away from your body. Oh, and they feel as comfy as a pair of new cotton undies. They hold up to 4 tampons’ worth of fluid and come in different lengths: Mini (8”), Maxi (10”), and Super (13”).

How to use:

Just snap the wings around your underwear with the tag facing down and bleed on (literally). Our pads absorb 8 times as much as a comparable disposable pad so you may find you need to change your pad less than usual. 

Once you’re finished with the pad rinse in cool water, then wash and dry with your regular laundry. Hang to dry where possible — it saves energy and prolongs the life of your products.

Best for:

  • Moderate to Heavy Flow
  • Strolls around town, or your 8th Zoom call of the day
  • Easy transition to reusables

Things to consider:

Since our reusable pads are the most similar to their disposable counterparts, these might be the easiest jumping-off point for your transition to reusables! They also have a lower price point, so you can try them out without breaking the bank in a big way. 

These work great for bladder leaks as well! And, if you’re looking for an overnight pad option, you definitely can’t go wrong with the Super

How do I make the move to sustainable products?

That was a hell of a lot of info. So if you’re feeling overwhelmed. We got you! Here’s our best advice for taking a step into the sustainable lane. 

Make it work for you:

Switching to reusables can feel like a big change with a big price tag so making sure you find a product that suits your current lifestyle, is the best way to secure success! 

Try to stick to what you know:

There’s pretty much a like-for-like when it comes to reusables. If you use pads, you can try reusable ones. Tampons? Maybe a menstrual cup! It’s best to flow in your lane when it comes to the switch, so whilst it might be tempting to go from 0 to menstrual cup, try a product that’s closer to the one you’re already using. 

Don’t go the whole blob:

If you do want to try something completely different — remember this doesn’t have to be an all-or-nothing situation. Start slow and ease your way into the sustainable flow. It’ll be better for your period and confidence if you try to slowly swap out your everyday products for sustainable ones.

Flow with the facts:

Aside from the environmental benefits of reduced monthly waste, reusable menstrual products are more comfortable and breathable, more convenient because you don't have to buy them every month and they also save money in the long run. Think of the benefits and the rest will flow. 

Don’t give up:

Maybe you don’t vibe with the first product you try — that’s ok! You can always try something that’s more suited to you and your flow. 

And most importantly — remember we’re here whenever you need us. We answer these questions every single day so you can always find what you need right here.

Which period product is right for me? 

Decisions, decisions, decisions. It’s not an easy choice, but we’re here to lend a hand. Here are all the facts laid out for you, so you can make an informed decision. Need help deciding? Take our Matchmaker Quiz and get synced up with the perfect product for you. Remember your body, your choice!



Easy to change? 

Ease of use 

Good for 

Maxi Pad 

8 tampons 



Fasten around underwear and wash after use

Moderate to heavy flow 

Super Pad 

14 tampons 



Fasten around underwear and wash after use

Heavy flow 


4 tampons



Fasten around underwear and wash after use

Light Flow

Extended Liner 

4 tampons 



Fasten around underwear and wash after use

Light Flow

Extra coverage 

Cup A

6 tampons /30ml



Insert and remove from vagina. Must be washed thoroughly. 

Moderate to heavy flow 

Cup B 

6 tampons /30ml



Insert and remove from the vagina. Must be washed thoroughly. 

Moderate to heavy flow 

BOOST period underwear

8—11 tampons 



Put the underwear on. Rinse and wash after use. 

Moderate to heavy flow

BOOST period thong 

1 tampon 



Put the underwear on. Rinse and wash after use. 

Light flow 

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