How Does Period Underwear Work? A Clear Guide for Hong Kong

Period underwear works by building the job of a pad directly into the underwear itself. Instead of adding a product to your day, the gusset is made of several bonded layers that pull moisture away from your skin, absorb the flow, and block it from reaching your clothes. You put it on in the morning like any other underwear, and it does the rest — no applicator, no adhesive, no timing it around a bathroom break.

That's the short answer. Here's what's actually happening underneath, and how to tell which pair is right for you.

The four layers, and what each one does

From the outside, a pair of Kiri period underwear looks like ordinary underwear. The difference is in the gusset, where four layers are bonded together:

• A moisture-wicking top layer — the part against your skin. It draws liquid downward almost instantly, so the surface stays feeling dry rather than wet.
• An antibacterial layer — neutralises the bacteria that cause odour, which is what keeps a pair feeling fresh across a full day.
• An absorbent core — the layer that holds the liquid. This is where capacity comes from: our daywear style holds up to 50ml, roughly 5.5 regular tampons' worth; the nightwear style holds up to 75ml, about 8.5 tampons.
• A leak-proof outer shield — a final water-resistant barrier so nothing reaches your clothes, even sitting or lying down.

None of these layers use dioxin, chlorine or rayon, so the fabric sitting against your skin has no reason to irritate it.

What it actually feels like

The most common thing customers tell us is that it feels like nothing. There's no bulk between your legs the way a pad has, and nothing to insert. On a moderate day, most people wear a single pair from morning to evening. On a heavier day, you change once — the same way you'd change underwear anyway — or wear it as leak-proof backup alongside a tampon or cup. It's built to work either way.

Day versus night: which to choose

The choice comes down to your flow and when you're wearing it. Daywear panties sit at a lower waist and handle light-to-moderate days on their own. Nightwear panties are cut higher with padding that runs all the way to the back of the waistband, so they hold up while you're lying down — that back coverage is the whole reason they work overnight. If your flow changes a lot across your cycle, a day-and-night bundle covers both without thinking about it.

One fitting note: the nightwear cut runs a little tighter than the daywear, so your size can differ between the two styles. If you're between sizes, go down a size. Our size guide walks through the underbust and waist measurements for each.

Built for Hong Kong's humidity

We're a Hong Kong team, and heat and humidity were part of the brief from the start. It isn't enough for the top layer to wick moisture from the inside — it also has to stay breathable against outside humidity so a pair never feels clammy on a 33-degree day. That's a different design problem from period underwear made for temperate climates, and it's the reason ours is drawn the way it is.

Caring for it (so it lasts years, not months)

Rinse under cold running water until it runs clear, machine wash cold inside a laundry bag, and line dry. No bleach, no fabric softener, no tumble dryer — heat and softener are the two things that shorten an absorbent layer's life. Cared for this way, one pair stays leak-proof and soft wash after wash for years, which is what makes the switch tend to be permanent.

Where to start

Most people only need one pair to understand what pads and tampons were missing. If you're new to it, start with a daywear pair toward the end of your next period, when your flow is lighter, and see how it feels. When you're ready to browse everything together, the full collection is here.