It's 3am, you're wide awake, and your underwear is the wettest part of you. You kick off the duvet, you might change your pyjama top, and then you get back into bed wearing the exact same underwear that started the whole problem in the first place.
Most of the advice out there focuses on room temperature, bedding and nightwear. Almost none of it mentions what's happening closest to your skin. If you're in perimenopause or menopause and dealing with hot flushes or night sweats, your underwear isn't a small detail. It's one of the few things you can actually control.
Here's what's going on, why it matters, and what to look for instead.
What's actually happening to your body (in plain English)
Perimenopause is the stretch of years before your periods stop altogether, often starting in your 40s, sometimes earlier. During this time, your oestrogen levels don't drop in a straight line. They swing up and down, sometimes within the same week.
Oestrogen has a role in how your body regulates temperature. When it fluctuates, the part of your brain that acts as your internal thermostat becomes more sensitive than usual. It can misread a small change in body temperature as overheating and trigger a rapid cooling response: your blood vessels widen, your skin flushes, and you sweat. That's a hot flush. At night, the same mechanism shows up as a night sweat, often intense enough to wake you.
This is a hormonal and neurological process, not a sign that anything is wrong with you, and it's one of the most common experiences of this life stage. It's also completely reasonable that the parts of your wardrobe touching your skin all night, or all day, would make a real difference to how manageable it feels.
Why synthetic fabrics make hot flushes and night sweats worse
A lot of everyday underwear is made from polyester, nylon or a cotton-synthetic blend. These fabrics don't breathe well, and they don't move moisture away from your skin. Once you start to sweat, it sits there.
That matters for two reasons. First, damp fabric traps heat against your body instead of letting it escape, so a hot flush takes longer to pass and feels more intense while it's happening. Second, damp skin doesn't stay comfortable. Skin that's slightly wet becomes tacky rather than slippery, so instead of fabric gliding over it, it grips and drags. If you're already prone to chafing between your thighs, a hot flush in synthetic underwear can make that worse too.
None of this is really about the fabric being "bad". It simply wasn't designed with rapid temperature swings and repeated sweating in mind, and during perimenopause, that's exactly what your underwear needs to cope with.
What to look for instead: breathability, moisture-wicking, a fit that doesn't dig in
If you're shopping for underwear with hot flushes and night sweats in mind, there are a few things worth prioritising over anything else:
- Breathable fabric. Something that lets air circulate rather than sealing heat in.
- A fabric that moves moisture rather than holding it. This is different from "waterproof" or "absorbent". You want moisture pulled away from your skin and given somewhere to go, so you're not lying in a damp patch until it evaporates on its own.
- A soft, wide waistband that doesn't dig in. Hormonal changes often bring bloating alongside hot flushes, so anything with a tight, narrow elastic can feel restrictive at exactly the wrong moment.
- Smooth seams that lie flat against the skin, rather than raised stitching that becomes irritating when your skin is already sensitive from sweating.
- A leg length that actually sits below where your thighs touch, if chafing is part of the picture for you too. A lot of everyday underwear stops a few inches down the thigh, which isn't always enough.
It's worth being sceptical of any underwear that claims to be antibacterial, hypoallergenic or somehow medically protective. Those are marketing claims, not something a fabric can substantiate. What you can actually judge for yourself is how it breathes, how it handles moisture, and how it fits.
The case for bamboo during this life stage
Bamboo viscose fabric has a few properties that make it a genuinely sensible choice for perimenopause and menopause, not because it's marketed at this life stage, but because of what it does mechanically.
It's breathable and temperature-regulating, so it doesn't trap heat against your skin the way a lot of synthetic fabric does. It moves moisture away rather than holding it against you, which matters enormously when you're dealing with sweating that can happen at any point in the day or night. It's also soft from the first wear, without needing to be broken in.
At Flissie, the boxer shorts are dyed to OEKO-TEX Standard 100, meaning they're independently tested for harmful substances. They come in a 6 inch leg for everyday wear or a 9 inch leg that sits just above the knee, which tends to suit hot weather, long days, or anyone who wants more coverage overnight. They're seamless at the back and sides, with a single flat seam at the front, so there's nothing raised digging into skin that's already had a long night. Sizing runs from UK 8 to UK 30, at one price across every size.
One Flissie customer, Georgia in the UK, put it simply: "They come to a good length to prevent chafe and are a lot cooler than my sports shorts." That's the effect you're looking for: less heat held against the skin, for longer.
If you want to understand the fabric science in more depth, including how bamboo compares to cotton, we've written about it here:
- Why bamboo fabric is better for sensitive skin
- Bamboo vs cotton: what two years of switching actually taught us
Beyond underwear: how the Hormonal Balance Supplement fits the picture
Underwear can only ever manage the external, physical side of a hot flush: how quickly heat and moisture move away from your skin. It doesn't do anything about the hormonal fluctuation causing the hot flush in the first place.
That's where a lot of women start looking at what they're doing from the inside as well, alongside the practical, physical changes like fabric and sleepwear. Flissie's Hormonal Balance Supplement was developed with that in mind, as one part of a wider approach to feeling more like yourself through a stage of change, rather than a stand-alone fix.
If you're considering a supplement, it's worth treating it the same way you'd treat any change during perimenopause: read what it actually contains, understand what it's intended to support, and have a conversation with your GP or a menopause specialist, particularly if you're on other medication or considering HRT. A supplement sits alongside medical advice, it doesn't replace it.
You can read the full product details here: Hormonal Balance Supplement.
FAQs
What's the best underwear for hot flushes? Look for breathable, moisture-wicking fabric with a soft, wide waistband and flat seams. Natural or semi-natural fibres like bamboo viscose tend to perform better than polyester or nylon blends, because they let air circulate and move sweat away from the skin instead of trapping it.
Does bamboo underwear actually help with night sweats? It helps with the experience of a night sweat, rather than preventing it. Because bamboo fabric is breathable and moves moisture away from your skin, a night sweat tends to feel less intense and pass more quickly, and you're not left lying in damp fabric until it dries.
Can perimenopause cause chafing? Indirectly, yes. Sweating more often, plus changes in body shape as hormone levels shift, can both make chafing more likely, even if it's never really been an issue for you before. Fabric that moves moisture away from the skin, and a longer leg length, both help.
What if my size keeps changing? It's genuinely common for bloating and weight distribution to shift during perimenopause. A wide, flat, soft waistband that doesn't rely on tight elastic will move with you more comfortably than a narrow one, so you're not having to size up and down every few weeks.
Is this the same as menopause underwear? "Perimenopause underwear" and "menopause underwear" describe the same practical need: fabric that handles hormonal hot flushes and night sweats well. Perimenopause is simply the transitional period before periods stop, and it's often when symptoms like this start showing up.
Shop Flissie: Shop the boxer shorts available in a 6 or 9 inch leg, UK 8 to 30, one price every size, with a 60 day comfort guarantee and a free swap on your whole first order. Or explore the Hormonal Balance Supplement.
