The short answer
For summer, pick the fabric by how the garment is built, not by the fibre name on the tag. A loose, thin, light-coloured single-layer knit or weave beats a dense one in the same fibre every time. Within that, the four fabrics worth considering behave differently enough to matter.
| Fabric | What it does well in heat | Where it falls down | Best used for |
|---|---|---|---|
| Cotton jersey | Absorbs sweat readily, washes hot, cheap to replace | Holds the damp once saturated and stays heavy against the skin | Everyday bodysuits and tees |
| Muslin (double gauze) | Very open weave, so air moves through it freely | Loses shape, snags, offers the least sun cover of the four | Swaddles, shade layers, pram covers |
| Linen | Stiff fibres hold the cloth off the skin, which is why it feels cool | Creases, harsher hand feel, rare in baby sizes | Occasion wear for older babies and toddlers |
| Bamboo viscose | Absorbs into the fibre and drapes thin and smooth | Weaker when wet, needs gentle washing, and is heavily over-claimed in marketing | Sleepwear and next-to-skin layers |
If you want one rule to carry around: in heat, thin and loose beats thick and clingy, and whatever the fibre, a second layer undoes most of the benefit of the first.
Why babies overheat faster than adults
A baby is not a small adult with the same thermostat. Two differences do most of the work.
The first is geometry. An infant has a large body surface area relative to body weight, several times that of an adult, which means heat moves in and out much faster than it would for you in the same room. Stanford Children’s Health puts this at roughly three times the adult ratio, which is why babies both chill and overheat quickly.
The second is control. Sweating is the body’s main way of shedding heat, and a newborn’s sweating response is immature. A baby cannot reliably sweat their way out of being overdressed, and cannot take off the layer you chose.
That combination is why overheating shows up as a modifiable risk factor in the American Academy of Pediatrics’ 2022 policy statement on sleep-related infant deaths, and why the same document advises dressing an infant in no more than one extra layer than an adult needs in that room. It is also why the useful check is the chest or the back of the neck rather than the hands and feet, which run cool in healthy babies and will tell you the opposite of the truth.
There is a corollary worth stating, because it changes what you buy rather than only what you worry about. Since the baby cannot shed a layer and cannot sweat efficiently, the fabric has to do a larger share of the work than it would for an adult in the same conditions. That is the whole reason this comparison is worth making at all — not because one fibre is magic, but because the margin for error is smaller.
What “breathable” actually measures
Breathable is used loosely in clothing copy, and it hides three separate properties that behave differently.
- Air permeability. How easily air passes through the cloth. This is mostly about the gaps: weave openness, knit structure and how tightly the yarn is packed. Muslin wins here by construction, not by fibre.
- Moisture absorption. How much water the fibre itself takes up. Cellulose fibres, including cotton, linen and bamboo viscose, absorb into the fibre. Polyester does not, which is why a synthetic tee can feel clammy while a cotton one feels merely damp.
- Drying rate. How fast the cloth gives that moisture back to the air. Here the absorbent fibres lose: cotton holds water longest, which is why a sweaty cotton vest stays cold and heavy.
No fabric is best at all three, and that is the reason the comparison table above has a column for weaknesses. What you want in summer is enough absorption to pull sweat off the skin, and enough air movement to get rid of it again.
This is also why two garments with the same fibre on the label can behave completely differently. A cotton interlock and a cotton gauze are both 100% cotton and they are not remotely the same garment in July. Any comparison that names only the fibre has dropped the variable that matters most.
Cotton, muslin, linen and bamboo viscose, compared
Cotton is the default for a reason. It absorbs well, tolerates a hot wash, survives being ruined, and costs little. Its weakness is the back half of the cycle: once a cotton knit is wet it stays wet, and a baby who has slept in a damp cotton vest wakes cold rather than cool.
Muslin is not a fibre. It is cotton in an open, usually double-gauze weave, and everything good about it comes from that structure. It is the most air-permeable of the four and the easiest to use as a shade layer. It is also the flimsiest, gives the least protection from sun, and goes out of shape quickly, which is why it belongs on swaddles and blankets rather than on garments that need to hold a fit.
Linen is the one people underrate. Flax fibres are stiff, so the cloth stands away from the skin instead of clinging, and that air gap is most of why linen feels cool. It absorbs well and releases moisture faster than cotton. The trade-offs are practical: it creases immediately, feels rougher against new skin until it has been washed a few times, and is uncommon below toddler sizes.
Bamboo viscose is a regenerated cellulose fibre, which is to say a rayon made from bamboo pulp. It absorbs into the fibre like other cellulosics, and the yarn spins fine and smooth, so the knits made from it are thin with good drape and very little surface friction. For a garment worn directly against skin for ten hours, that smoothness and thinness are the real advantages. They are also enough, which is fortunate, because the claims usually stacked on top of them are not supportable.
Where bamboo wins for summer babies, and where it does not
The honest version of this comparison has a scope attached to it, because bamboo viscose does not win every summer question. It wins one of them clearly, and that one happens to be the question most parents are actually asking.
It wins for the layer worn directly against skin, for hours at a time. Three properties combine there and no other fibre in this group has all three: the knit spins thin, the surface is smooth enough to produce very little friction, and the fibre absorbs moisture into itself rather than leaving it on the skin. For a sleepsuit worn ten hours in a warm room, or a bodysuit worn under everything else, that is the right set of properties. It is why the fabric dominates baby sleepwear and why we use it for ours.
It loses on raw air movement. An open cotton double gauze moves more air than a bamboo jersey does, because air permeability is decided by the gaps in the cloth and gauze has more of them. If the job is a shade layer over a pram or a swaddle in a hot room, muslin is the better fabric and it is not close.
It loses on wash tolerance. Summer means more washing, and regenerated cellulose is weakest when wet. A cotton bodysuit can go through a 60 °C cycle after a hot-weather nappy leak; a bamboo one should not. Over a hot summer that difference compounds.
It loses on sun cover, at equal weight. A thin, pale bamboo knit is a poor UV barrier, and thinness is exactly what you chose it for. For time outdoors, the garment you want is denser and darker, whatever the fibre.
So the useful framing is not which fabric is best but which layer you are buying. Next to the skin, bamboo viscose. Over the top for shade, muslin. Out in the sun, a denser weave in a deeper colour. For the load that gets properly dirty, cotton.
The claims about bamboo that do not hold up
This category has a marketing problem, and it is worth being specific about it rather than repeating the claims and hoping.
Antibacterial. Bamboo the plant contains compounds sometimes described as antimicrobial. Bamboo viscose fabric has been dissolved in chemicals and regenerated, and the Federal Trade Commission’s position is that this processing destroys the properties of the original plant. Claims that the finished textile is antibacterial or odour-resistant need evidence about the finished textile. We do not make that claim.
“Twenty per cent more breathable than cotton” and similar figures. Numbers like this circulate without a test method attached, which makes them meaningless: air permeability depends on the knit, the yarn count and the finishing, so a dense bamboo interlock is less breathable than an open cotton gauze. A figure comparing two fibres without specifying the fabric is comparing nothing.
“Stays three degrees cooler against the skin.” A fabric does not have a temperature of its own. What varies is how quickly heat and moisture leave the skin underneath it, which depends on the room, the airflow, the number of layers and how hard the child is working. A single number detached from all four is not a measurement of anything.
Eco-friendly. Converting bamboo into viscose uses toxic chemicals and produces hazardous pollutants. That was one of the grounds for the FTC’s April 2022 settlements with Kohl’s and Walmart, which carried civil penalties of 2.5 million and 3 million dollars. Bamboo lyocell, produced in a closed-loop solvent process, has a genuinely better environmental profile than bamboo viscose, and the two should not be described interchangeably.
Hypoallergenic. There is no regulatory definition of the word for textiles. What a smooth, thin, low-friction fabric can do is avoid two known irritants, which are rubbing and trapped sweat. That is a real benefit and a smaller claim.
The labelling rule follows from the same place: a garment made this way must be identified as rayon or viscose, optionally as “rayon made from bamboo”. In the EU, Regulation (EU) No 1007/2011 requires the generic fibre name in the same way, and the permitted name is viscose. If you see a soft knit labelled 100% bamboo in either market, the seller has a compliance problem.
How to judge a summer baby fabric with your hands
None of the properties above are printed on a baby garment, and the marketing copy is the least reliable source in the room. These four checks take under a minute and tell you more than the fibre name does.
- Hold it up to a window. The amount of light through the cloth tracks both air permeability and UV protection, in opposite directions. Lots of light through means cool and poor sun cover. Very little means the reverse. This single test sorts most of the confusion.
- Drape it over your forearm. A summer fabric should fall away from skin rather than cling to it. Cloth that clings has more contact area, and contact area is how heat transfers in.
- Scrunch it and let go. Fabric that springs back has body and will hold its shape off the skin. Fabric that stays crumpled will sit flat against the child. Linen is the exception here: it creases badly and still holds itself off the skin, because the fibre is stiff.
- Look at the inside face, at a seam. Overlocked seams with a raised ridge sit in the neck and armpit, which are exactly where heat rash starts. Flat seams are worth more in summer than in winter.
The same four checks are how to compare two garments from different sellers in the same fibre, which is a more common problem than choosing between fibres. The spread of quality within cotton jersey alone is wider than the gap between cotton and bamboo.
Colour: white is not automatically the coolest choice
The received wisdom is to dress a baby in white in summer, and it is half right in a way worth unpacking, because the two halves point in opposite directions.
Pale colours reflect more visible and near-infrared light, so a white garment in direct sun heats up less than a black one. That part of the folk wisdom is sound, and it is why pale linen is a hot-climate tradition.
Darker, more saturated dyes absorb more ultraviolet, which means they let less of it through to the skin. At the same weight and weave, a navy or deep red cloth gives better UV protection than a white one.
So the two effects trade against each other, and which one matters depends on where the child is:
- Indoors or in full shade, UV is not the issue and pale is the cooler choice.
- Out in direct sun, sun protection is the priority and a deeper colour in a loose cut is better than a white one in the same cut. Loose is what keeps it from being hot.
- In and out of shade all day, which is most days, a mid-tone in an open weave is the sensible compromise, with shade and a brimmed hat carrying the real load.
Two smaller points follow. A wet garment protects less than a dry one, so a soaked pale tee over a paddling pool is close to no protection at all. And a garment stretched tight over a toddler’s stomach opens the gaps in the cloth, which is another argument for buying loose in summer rather than fitted.
Sun protection is a construction question, not a fibre question
UPF describes how much ultraviolet radiation a fabric lets through to the skin. It is a property of a specific piece of cloth, and it moves with things that have nothing to do with the fibre name.
- Tightness of weave or knit. The single largest factor. Gaps let UV through.
- Weight and thickness. Heavier cloth blocks more.
- Colour. Darker and more saturated dyes absorb more UV than pale ones.
- Stretch and moisture. A fabric stretched over a toddler’s stomach, or wet from a paddling pool, protects measurably less than the same fabric dry and relaxed.
Textile research has compared regenerated cellulose fibres with cotton at matched yarn counts and found differences, so the fibre is not irrelevant. But it is second-order. A loose pale bamboo gauze protects less than a dense navy cotton tee, and neither should be assumed to carry a UPF rating unless the garment is tested and labelled with one.
For babies the clothing question also sits downstream of a simpler one. The AAP advises keeping infants under six months out of direct sunlight and using clothing and shade as the first line of protection, with sunscreen on small exposed areas only where shade and clothing are not enough. Long sleeves, a wide brim and staying out of midday sun do more than any fibre choice. Where a garment is sold with a tested UPF rating, as our swim range is, that number belongs to that garment and not to the fibre in general. What the rating does and does not cover is set out in what a UPF 50+ rating actually means.
The second-layer problem: prams, carriers and car seats
Most summer overheating does not happen in a cot. It happens in the three places where an adult has added something on top of a sensible outfit, and each has its own failure mode.
The pram. Draping a muslin or blanket over the opening for shade restricts the air exchange that was keeping the space cool, turning a shaded pram into an enclosed one. Use a clip-on shade or a parasol that leaves the opening clear, and check the child rather than assuming the shade is working.
The carrier or sling. A carried baby is pressed against an adult body at roughly 37 °C across a large contact area, which is an additional heat source that no fabric can offset. In practice a baby in a carrier needs one layer fewer than the same baby in a pram, and the contact area — chest, stomach, inner arms — is where to check the temperature afterwards.
The car seat. A parked car heats up fast, and the harness and seat shell hold heat against a child once you set off. The habit that helps is to dress for the car rather than for the pavement: thin layers under the harness, warmth or shade added on top afterwards, and a check of the buckle and the seat surface with your hand before the child goes in on a hot day.
Across all three, the common error is the same: someone adds a layer for a reason that made sense (shade, wind, the walk from the car) and nobody removes it when the reason stops applying. Sixty seconds of undressing at the destination prevents more overheating than any fabric choice.
What to dress a baby in, by temperature
Work from a thermometer in the room the baby is actually in, because indoor temperature tracks the season poorly.
| Conditions | Daytime | Sleep |
|---|---|---|
| Above 27 °C (80 °F) | Short-sleeve bodysuit or a loose romper, nappy plus one layer indoors | Short-sleeve bodysuit alone, no sack |
| 24–27 °C (75–80 °F) | Single light layer, bare arms and legs in shade | Short-sleeve bodysuit, or a 0.5 tog sack over one |
| 20–23 °C (69–74 °F) | Light long sleeves, or short sleeves with a muslin to hand | Long-sleeve sleepwear, or a bodysuit under a 1.0 tog sack |
| Outdoors in sun | Loose long sleeves, a brimmed hat, and shade rather than more fabric | — |
Two habits matter more than the chart. Check the chest or the nape of the neck by hand every few hours in hot weather. And put the room thermometer where the baby sleeps rather than on a shelf by the window, because the two readings can differ by several degrees.
Heat rash: what clothing can and cannot do
Heat rash is blocked sweat ducts, which is why it appears where skin is covered, creased or pressed against fabric. The neck, upper chest, armpits and nappy line are the usual sites. It presents as clusters of tiny bumps and clears on its own once the skin cools and dries.
Clothing choices that reduce the odds are unglamorous and consistent: fewer layers, looser cut, no plastic-backed changing mat against bare skin for long periods, and a change of clothes after a sweaty nap rather than letting a damp layer dry on the child. Fabric plays a supporting role here, and the fibre argument is far less important than the number of layers.
Two construction details do earn their place, because they act on the specific sites where it appears:
- Flat seams at the neck and armpit. A raised overlocked ridge sits in the crease and holds damp against it.
- Nothing elasticated across the chest or the upper arm. Elastic creates a line of continuous pressure and a channel where sweat pools, and it is a common trigger on summer dresses and rompers.
If a rash is not clearing, is weeping, or comes with a fever, that is a question for a clinician rather than for a fabric guide. For a child who flares regularly rather than only in heat, the construction details that matter most, and the washing routine behind them, are set out in what to check on sleepwear for sensitive skin.
Washing summer fabrics without wrecking them
Summer triples the wash load, and each of these four fabrics fails in a different way under that.
| Fabric | Wash | What goes wrong if you do not |
|---|---|---|
| Cotton jersey | Up to 60 °C when needed, dry low | Little. This is the robust one; the risk is shrinkage from dryer heat rather than from washing |
| Muslin | 40 °C, wash bagged or separately | The open weave snags on zips and hooks, and a snag becomes a hole in one cycle |
| Linen | 40 °C, line dry slightly damp | Hot drying sets creases hard and makes the fabric brittle over a season |
| Bamboo viscose | 30 °C, gentle, inside out, dry low | Thinning and pilling at knees and elbows within a season, because the fibre is weakest wet |
Two rules apply to all four in hot weather. Skip fabric softener, which coats fibres and reduces exactly the absorbency you bought them for. And do not let a sweaty garment sit damp in a basket overnight, which is how summer clothes acquire the odour that survives washing. The full routine is in how to wash baby clothes.
Certifications: what OEKO-TEX and GOTS each cover
These two get used as though they were interchangeable quality marks. They certify different things, and knowing which is which stops you paying for the wrong reassurance.
| What it certifies | What it does not tell you | |
|---|---|---|
| OEKO-TEX Standard 100 | The finished article has been tested against a list of substances harmful to health. Class I is the strictest tier and applies to articles for babies and toddlers. | Nothing about organic content, farming, labour conditions, or how the fabric performs |
| GOTS | Organic fibre content plus environmental and social criteria across processing, from fibre to finished garment | Applies to natural fibres, so it is not available for bamboo viscose at all |
That last row is the practical one. If a bamboo viscose garment is advertised as GOTS certified, something is wrong, because GOTS covers organic natural fibres and viscose is a regenerated one. For bamboo, OEKO-TEX Standard 100 is the certification that applies. For organic cotton, GOTS is the stronger of the two, and our organic cotton range is where that matters.
Neither certification tells you anything about breathability, and neither is a substitute for the four hand checks above. They are about what is in the fabric, not about how it performs in July.
What this guide does not claim
We did not run air-permeability, drying-rate or UPF tests for this article. The fabric behaviour described here is general textile science, and where a specific garment carries a tested rating, that rating is printed on the garment rather than inferred from its fibre.
We also make no antibacterial, odour-resistant or hypoallergenic claim for bamboo viscose, and no environmental claim for it beyond noting that lyocell processing is a closed loop and viscose processing is not.
If you want thin summer layers, our bamboo baby clothes and baby clothes ranges both carry single-layer pieces in the cuts described above, and the measurements behind every size are on the PatPat size chart. How the same fabrics behave overnight, when the trade is warmth against breathability, is covered in bamboo versus fleece for baby sleepwear.
Frequently asked questions
What is the most breathable fabric for baby clothes in summer? Muslin, because the open double-gauze weave moves the most air. For clothes rather than blankets, a thin single-layer cotton or bamboo viscose knit is the practical answer.
Is bamboo better than cotton for a baby in summer? For the layer worn against skin, yes, because it spins thinner and smoother. For anything that needs a hot wash or has to stand up to sun, cotton is the better choice.
Is bamboo fabric antibacterial? No. The FTC's position is that processing bamboo into viscose destroys the properties of the plant, so the finished fabric should not be sold on that basis.
Does bamboo fabric block UV? Only as much as its weave, weight and colour allow. UPF belongs to a specific tested garment, not to a fibre, and a loose pale knit of any fibre protects poorly.
Should I dress my baby in white in summer? In shade or indoors, yes, because pale reflects more heat. In direct sun a deeper colour in a loose cut protects better, since darker dyes absorb more UV.
What should a baby wear to sleep in summer? A single short-sleeve layer above 24 °C and nothing over it. Add a 0.5 tog sack only if the room drops, and check the chest rather than the hands.
How do I stop my baby getting heat rash? Fewer layers, looser cut, and a change of clothes after a sweaty nap rather than letting the damp layer dry on them. Heat rash is blocked sweat ducts, so the fix is cooling and drying the skin.
Can I put a blanket over the pram for shade? No, it traps heat inside. Use a clip-on shade or a parasol that leaves the opening clear.
Does a baby in a carrier need fewer layers? Yes, usually one fewer. The adult body is a continuous heat source across a large contact area, and no fabric offsets that.
How should I wash bamboo baby clothes in summer? Cool at 30 °C, gentle cycle, inside out, dried low. The fibre is weakest when wet, so hot washing is what thins it within a season.
Is GOTS certification available for bamboo clothing? No. GOTS covers organic natural fibres and bamboo viscose is a regenerated fibre, so the relevant certification for bamboo is OEKO-TEX Standard 100.
How do I know if my baby is too hot? Feel the chest or the back of the neck, never the hands or feet. Sweating, damp hair or a hot chest means remove a layer.
About this article
Written and fact-checked by the PatPat Editorial Team. How we research, source and review what we publish is set out on our editorial standards page.
Method. No fabrics were tested for this article. Fibre and construction behaviour described here is general textile science rather than measurement of our own products, and no UPF figure is attributed to any PatPat garment except where that garment is tested and labelled.
Sources. Infant surface-area-to-weight ratio: Stanford Children’s Health. Overheating as a risk factor and layering guidance: AAP, Sleep-Related Infant Deaths, 2022 policy statement and A Parent’s Guide to Safe Sleep. Sun protection for infants: AAP, Sun Safety. Car seats and bulky layers: AAP, car seat safety. Bamboo labelling and claim substantiation: FTC, Bamboo Textiles and the April 2022 Kohl’s and Walmart settlements. EU fibre naming: Regulation (EU) No 1007/2011. Certification scope: OEKO-TEX Standard 100 and Global Organic Textile Standard.
This is not medical advice. A rash that is not clearing, is weeping, or comes with a fever needs a clinician, not a change of clothes.
Corrections. An earlier version of this article, published in 2026, described bamboo fabric as naturally antibacterial and hypoallergenic, stated that it is about 20% more breathable than cotton and stays about three degrees cooler against the skin, and attributed UPF 50+ protection to the fibre. None of those claims were supportable and all have been removed.
Last updated 17 September 2026 · Next review May 2027, before the summer season
