What Are Period Pants Made Of? Materials Explained

What are period pants made of?

A typical pair of period pants combines an everyday underwear fabric for the body with a gusset of three or four technical layers, and the fibres in each part are chosen for a different job. The body is there for fit and feel. The gusset is there to absorb and block.

In the UK brands that publish their fibres, the body fabric is cotton or organic cotton, bamboo viscose, nylon (also called polyamide) or a wood-pulp fibre such as Tencel modal or lyocell, each blended with a little elastane or spandex for stretch. Annahitah’s twelve styles span organic cotton (Valentina, Lilah, Venus, Eden), bamboo (Serendipity, Gaia) and nylon (Shanti, Odessa, Athena, Aurora, Luna, Nirvana), always with 5 to 15 percent elastane or spandex. The brand says its range includes recycled nylon, though the site doesn’t say which styles use it.

The gusset is where the engineering sits, and it’s rarely made of the same fibre as the body.

What is each layer made from?

Each layer in the gusset uses a fibre picked for one task, so a single pair can contain cotton, polyester and polyurethane within a few millimetres of each other. The table maps the common fibres to what they do.

What is the top layer made from?

The top layer, the one against your skin, is cotton, organic cotton, bamboo viscose, modal or merino in the UK brands that publish their fibres, because these feel soft next to skin. One uses organic cotton here, another merino, another Tencel modal blended with elastane. The job is to pull fluid down and away fast.

What is the absorbent core made from?

Absorbent cores in UK brands are polyester microfibre, cotton/elastane, bamboo, merino or recycled nylon, depending on the brand. Brand A’s Super Heavy core is 88 percent polyester with elastane. Brand B uses cotton/elastane or bamboo. Brand C uses microfibre, merino or recycled nylon, and Brand D microfibre. Annahitah describes its middle layers as absorbent and breathable without naming the fibre on its site, so we won’t name one either.

What is the waterproof layer made from?

The waterproof layer is polyurethane, applied either as PUL (polyurethane laminate, a fabric pre-coated with a polyurethane film) or TPU (thermoplastic polyurethane, a thin film bonded between layers). Some name PUL, others TPU, and others simply list polyurethane in the gusset. Both forms block liquid while letting water vapour through, which is why period pants don’t feel like a nappy. Brands cap wash temperatures to protect this layer; Annahitah asks for 30°C.

Do period pants contain plastic?

Yes, almost all period pants contain some plastic, because the leak-proof barrier is polyurethane and the stretch comes from elastane, both synthetic. A pair with a 95 percent organic cotton body still has a polyurethane layer in the gusset. That’s not a flaw. It’s the part doing the blocking.

Some brands describe their pants as plastic-free. Be careful with that phrase. Brand B’s shop page uses it, while Brand B’s own how-it-works page names TPU as its waterproof layer. The honest position is that period pants reduce plastic by replacing hundreds of disposable pads and tampons, not that they contain none. Annahitah makes no plastic-free claim.

If you want as little synthetic as possible against your skin, choose a style with a cotton or bamboo body, such as Annahitah’s Valentina (95 percent organic cotton) or Serendipity (94 percent bamboo). The barrier is still there, but it sits beneath the absorbent layers rather than on your skin.

Bamboo vs cotton period pants: which is better?

Neither is better across the board: cotton is the fibre the NHS names for underwear if you’re prone to thrush, while bamboo viscose is sold on softness and a cool feel. The right one depends on your skin and what you like against it.

Cotton’s case is simple. NHS thrush guidance says to wear cotton underwear, and its vaginitis guidance says loose cotton underwear. It’s familiar, and it’s the fibre with public health advice behind it.

Bamboo’s case is comfort. Bamboo fabric is bamboo viscose, a fibre made from bamboo pulp rather than the raw plant, and brands sell it on how smooth and cool it feels. Some brands also say bamboo has natural antibacterial properties. Treat that as a brand claim rather than a proven benefit.

Annahitah offers both. Valentina, Lilah, Venus and Eden are organic cotton bodies; Serendipity and Gaia are bamboo. If you’ve had thrush or irritation before, start with cotton. If you want the softest feel, try bamboo.

Is nylon or recycled nylon safe to wear as underwear?

Yes, nylon has been used in underwear for decades, and the questions people raise about it concern finishes added to the fabric and microfibre shedding rather than the fibre itself. Half of Annahitah’s styles, among them Shanti, Odessa, Luna and Nirvana, have nylon bodies.

Nylon earns its place in period pants because it’s thin, strong and stretchy and knits without seams. It’s why a Super Heavy pair such as Odessa can be high-waisted and still disappear under leggings. Its downside is environmental: it’s a synthetic that sheds microfibres in the wash.

Recycled nylon, sold under names such as ECONYL, is rebuilt from waste such as fishing nets and old carpet. It’s the same fibre once made, so it wears and feels the same; it still sheds microfibres and still won’t biodegrade. Annahitah says its range includes recycled nylon but doesn’t say which styles, so we don’t label any one pair recycled. The health questions around any synthetic underwear concern the dyes and finishes applied to it, which is where certification comes in.

What do GOTS and OEKO-TEX STANDARD 100 certify?

GOTS certifies that a textile’s fibre is organic and that every stage of processing from the farm gate to the shop meets environmental and social rules, while OEKO-TEX STANDARD 100 tests a finished textile and all its components for harmful substances. They answer different questions, and neither covers everything.

Annahitah’s suppliers are GOTS and OEKO-TEX certified. That is the accurate wording, and it’s different from saying the finished pants carry a GOTS label. GOTS is about the organic fibre and its processing chain; OEKO-TEX is about what’s left in the fabric when it reaches you. When a brand’s suppliers hold both, the fibre came through an audited organic chain and the fabric was tested for harmful residues before it was sewn. If you’re choosing between brands on OEKO-TEX certified materials, ask whether the certificate applies to the supplier, the fabric or the finished garment, because all three are possible and all three are different.

What about silver and PFAS in period pants?

Some UK brands add silver to the gusset as an antimicrobial, and Which? found it in several pairs when it tested period pants in November 2023, at levels from under 1 mg/kg to over 100 mg/kg. Annahitah uses no silver in any style; where it adds an odour-control agent, that agent is silver-free. PFAS are a separate concern, covered by OEKO-TEX’s 2023 ban on intentional use but not proven absent by any supplier certificate, and Annahitah makes no PFAS-free claim.

What is the best fabric for period underwear?

There’s no single best fabric; the right choice balances skin comfort, how invisible you need the pants to be and how heavy your flow is. The gusset layers are chosen by the brand. What you choose is the body fabric and, through it, the style.

A rough guide:

• Sensitive skin or a history of thrush: an organic cotton body, such as Valentina or Lilah.
• The softest feel: bamboo, such as Serendipity or Gaia.
• Leggings, gymwear, no visible lines: a nylon seamless style, such as Odessa, Luna or Nirvana.
• Heaviest days: the fibre matters less than the absorbency level. Annahitah’s Super Heavy range covers cotton (Valentina) and nylon (Shanti, Odessa, Athena).

Whatever the body fabric, the care is the same: cold rinse, 30°C wash, no softener, no bleach, hang to dry. Annahitah’s own care page says softener and bleach affect absorbency and the four-layer construction, and hot washes are what brands warn against for the barrier.