Period underwear is the fastest-growing menstrual care category in Spain, and it’s no coincidence: it’s ordinary underwear with invisible absorbent technology that replaces (or backs up) pads and tampons. In this guide we explain how its layers work, how to choose absorbency and size, how to wash it so it lasts for years, and when to combine it with a menstrual cup. With concrete data and no inflated promises.
If you’ve made it this far, you’re probably considering the switch and a few reasonable doubts are holding you back: does it really absorb? Does it smell? How many do I need? Is it worth the price? Let’s answer them all, starting from the beginning.
On the outside, ordinary underwear. On the inside, a four-layer system sewn into the gusset that absorbs the flow, holds it and prevents leaks and odors. The difference from a pad is radical: nothing moves, nothing rubs, nothing rustles, and at the end of the day you wash it and reuse it for years.
The top layer wicks the flow into the absorbent core and stays dry to the touch; the core holds the equivalent of 2-3 tampons depending on the model; a waterproof but breathable membrane prevents leaks; and the outer fabric is cotton, like your everyday underwear. In Sileu period underwear, the cotton is organic and certified to OEKO-TEX Standard 100, the international textile label that guarantees fabrics free from harmful substances — something worth insisting on in a garment that will be in contact with your skin for hours.
The average user spends €5-10 a month on disposable pads or tampons. Period underwear costing €9.99 that lasts 2-3 years of washing pays for itself in the first month or two. Add to that what can’t be measured in euros: sleeping without the feeling of “wearing something”, zero plastic in the bin and zero disruptors in contact with your skin (we tell you more in our article on what pad and tampon marketing doesn’t tell you).
The weak point? With very heavy flow, underwear alone may not be enough on heavy days. That’s where the combo with the cup comes in, which we cover below.
Sileu organic cotton period underwear — €9.99
Made of certified organic cotton (OEKO-TEX Standard 100), reusable, breathable and hypoallergenic. It pays for itself in the first month compared with disposable pads, and ships from Spain in 24-72h.
The rule of thumb: think about what you’d use that day if you wore tampons.
If you don’t use a cup yet and want to take the step, our guide to choosing your first menstrual cup walks you through it; and if you’re coming from tampons, here we explain how to make the transition without stress.
Use your usual underwear size: period underwear should fit snugly (without squeezing) so the absorbent area is always in contact with your body. If you’re between two sizes, choose the smaller one: loose underwear loses its leak protection. Sileu underwear follows standard European sizing; you’ll find the exact measurements on the product page.
To use them as your main method you need a rotation: while some are being washed and dried (air-drying takes time), others are in use. The realistic count:
Starting with 2 and adding more once you see how they fit your cycle is the most sensible strategy (and the one that risks the least money: €19.98). We do the full calculation in how many period panties do I need?
With this care, quality period underwear lasts 2 to 3 years of regular use. If you notice it absorbs less or smells after washing, it’s a sign it needs replacing (or that some softener slipped into the wash).
If you want the full detail, with a step-by-step routine, hand washing and solutions to absorbency or odor problems, we have a specific guide: how to wash period panties so they last for years.
One of the things our customers tell us most is that they end up using their period underwear far beyond their period. These are the scenarios where it performs best:
The market is full of period underwear at every price, and not all of it is the same. Four things worth checking, whatever the brand:
Sileu underwear meets all four points, and the price (€9.99, or €18.49 for a pack of 3) is possible because we sell factory-direct, without intermediaries.
Most of our long-time customers end up in the same place: cup inside, underwear outside. The cup collects the flow for up to 8-12 hours and the underwear removes the one remaining fear (what if something leaks when I empty it late, exercise or sleep?). It’s also the favorite combination for the beach and the pool — underwear for before and after the water — and for postpartum, when the cup can’t be used yet. We’ve put both together in the period underwear + Sileu Rose cup pack.
It depends on your flow and the absorbency: with light flow it can cover up to 12 hours; with medium flow, a 6-8 hour day. At first it’s a good idea to check it halfway through the day until you know your rhythm.
No, if it’s changed and washed correctly: the wicking layer keeps moisture away from your skin and the flow is held in the core. Odor only appears after far more hours than recommended, or if fabric softener has damaged the absorbent fabric.
Yes, with light or medium flow and a rotation of 4-6 pairs. With heavy flow it works better as backup to a menstrual cup on heavy days and as your only method on lighter days.
Between 2 and 3 years of regular use if washed at 30 °C without fabric softener, bleach or tumble drying. At €9.99, the real cost is far below a single year of disposable pads.
Start the leak-free duo today
Sileu organic cotton period underwear (€9.99) + Sileu Classic cup (€14.99): complete day and night protection for under €25, shipped from Spain.
Keep reading:
“I washed them like any other underwear and within a few months they didn’t absorb the same”: it’s the number-one reason people are disappointed with
“I’ve had the same cup for three years, should I replace it now?” It’s a question we get often, and the honest answer is: it
We sell menstrual cups, so you’d expect this article to tell you the cup is perfect for everyone. It isn’t, and we’d rather tell you
