Why Natural Mattresses and Tatami Mats Sometimes Smell at First

Natural bedding can be one of the cleanest, most comfortable ways to sleep, but it can also surprise people during the first days after delivery. A common theme in customer feedback is the contrast between expectations and reality: some shoppers describe a strong “new” odor lingering for a week or more, while others are relieved to find “no unpleasant smells at all.”

The truth is that natural materials have natural aromas, and those aromas can be intensified by compression, plastic wrapping, shipping conditions, and room humidity. In most cases, the smell is temporary and fades with ventilation. In a smaller set of cases, the odor points to moisture exposure and needs attention.

This guide explains what causes the smells most people notice in cotton-core mattresses (including models with wool, latex, and foam layers) and tatami mats, what a normal break-in looks like, and how to get the best results with a simple 2–3 week airing routine. If you’re shopping for a healthier setup, start with our natural sleep options and build the rest of the room with breathable bedding layers.

What “new mattress smell” means for natural materials

When people hear “new mattress smell,” they often assume it’s chemical off-gassing. With natural bedding, it’s usually something else:

• Concentrated natural fiber scent trapped inside sealed plastic
• Plant-based aroma from minimally processed fibers (cotton, wool, rush grass)
• Moisture and temperature swings during transit that amplify odor
• Natural latex scent (rubbery, vanilla-like to some)
  

A key point: natural does not mean odorless. Cotton, wool, and rush grass are agricultural materials. They can smell “earthy,” “barn-like,” “hay-like,” “sweet,” or “grassy” depending on the fiber and how it was processed.

Why the smell can feel stronger after shipping

Compression and sealed plastic make everything more intense

Many mattresses and some tatami-style products ship compressed or tightly wrapped in plastic. That does two things:

1. It traps volatile compounds and humidity so the scent has nowhere to go.
2. It creates a “first release” effect: once opened, all trapped odor exits at once.

That same compression is also why people sometimes notice lumps, unevenness, or waviness at first. This is typically not a defect.

What to expect in the first 48–72 hours

• The smell often peaks within the first several hours after unboxing.
• The surface may look uneven or feel slightly lumpy from compression.
• Both the odor and the “settling in” improve as the product expands and breathes.

If your product was rolled, vacuum-packed, or boxed, it’s reasonable to set expectations that the first 2–3 days are the most noticeable.

Cotton-core mattresses: what causes that “cotton” smell

Cotton batting used in mattresses can have a distinctive aroma, especially when it’s less processed (not heavily bleached or deodorized). Common contributors include:

• Natural waxes and plant compounds that remain in cotton fiber
• Cotton “motes” or tiny plant particles that are harmless but aromatic
• The general scent of a fresh textile that has been sealed and compressed

Some people describe it as clean and “plant-like,” while others interpret it as sharp, dusty, or stale. Sensitivity varies. If you’re comparing builds (cotton-only vs. cotton-and-wool vs. cotton with latex or foam), you’ll usually see the widest range of first-week scent reports in our mattress lineup, simply because each layer has its own natural signature.

When cotton smell lingers

A week can still be within normal range, especially if:

• The room is closed up (winter, A/C running, windows rarely opened)
• Humidity is elevated
• A waterproof protector went on immediately (this can trap odor)
• The mattress is on the floor (reduces airflow beneath)

For best results, treat the first days as a “breathing period,” not the final state.

Wool layers: earthy, lanolin, and “wet wool” notes

Wool often has the most recognizable natural scent in bedding. Depending on the wool type and wash/scouring process, you may notice:

• Earthy or “farm” aroma
• Lanolin-like warmth (sometimes described as sweet or oily)
• A temporary “wet wool” impression, especially if humidity is high

Wool smell usually fades with airflow and time, but it can reappear slightly on damp days because wool naturally interacts with moisture.

Natural latex: the “rubbery” or vanilla-like scent

If your cotton-core mattress includes natural latex, it may have a noticeable odor on day one. People describe it in different ways:

• Rubber/balloon
• Vanilla-like
• Sweet, warm, or “new tire” (less common with higher-quality latex but still possible)

Latex scent typically reduces steadily with ventilation. If you’re dealing with a latex layer, the 2–3 week break-in and airing window is a realistic expectation for best results, especially for scent-sensitive sleepers.

Foam layers: what to know

Some cotton-core mattresses include foam layers for pressure relief or structure. Depending on the foam type, you may notice more conventional “new product” odor during the first days.

Important nuance: not all foam smell is the same. Some foams have very little odor; others are more noticeable right out of the wrapper. Ventilation matters, and so does the amount of foam relative to the overall mattress.

If your design includes foam, it’s even more helpful to recommend:

• 48–72 hours of strong airflow after unboxing
• A 2–3 week break-in period for best overall results (feel and scent)

Tatami mats: natural grass smell vs. musty or moldy odor

Tatami and tatami-style mats often use rush grass (igusa) or other plant fibers. A natural tatami aroma is typically grassy, green/earthy, and similar to dried hay or straw. It’s noticeable when new, then becomes more subtle over time. If you’re pairing your sleep setup with traditional surfaces, explore Japanese-style floor mats and low-profile frames like platforms designed for tatami.

If you want a deeper breakdown of what creates tatami scent (and how color and aroma change as mats age), see: our tatami materials guide.

That said, some reviews describe odors that are not “normal tatami,” including “moldy,” “rotting plant,” or lingering mustiness even after weeks. Those descriptions point to a different issue: moisture exposure.

Why tatami-like products can smell “moldy”

Plant fibers can absorb moisture during:

• Ocean freight or long-distance transit
• Warehouse storage in humid environments
• Delivery during rainy periods
• Being placed on a cold floor without airflow

When moisture gets trapped in packaging, the product can develop a musty smell. Sometimes it’s just damp fiber odor that resolves as it dries. Other times, it can signal actual mildew growth.

Related reading: mattress airflow and mold prevention.

What’s normal vs. what’s a red flag

Typically normal (improves with time)

• Cottony, dusty-textile, or mild earthy smell
• Wooly/lanolin “farm” notes
• Latex rubbery/vanilla scent
• Grassy tatami aroma
• Odor that steadily decreases day by day

Concerning (needs action)

• Strong mildew smell described as “basement,” “mold,” or “rotting plant”
• Odor that does not improve or gets worse after several days of airing
• Visible damp spots, discoloration, or any fuzzy growth
• Any sign the product arrived wet or was stored in a damp space

A helpful way to frame this for customers: natural scent is expected, but mildew-style odor is not.

The break-in period: why 2–3 weeks is a smart expectation

Even when odor fades quickly, comfort and feel can change over the first couple weeks. Natural fibers settle, loft changes slightly, and layers “find” their resting alignment after compression.

A clear expectation statement you can safely make:

• First 48–72 hours: expansion, airflow, and the most noticeable scent release
• First 2–3 weeks: best results for scent reduction and overall “broken-in” feel

This doesn’t mean customers can’t sleep on it right away. It means the product may not feel or smell like its “final” state on day one.

How to air out a natural mattress for best results

Step-by-step airing routine (simple and effective)

1. Unwrap completely and remove all plastic from the room if possible.
2. Place the mattress on a breathable base such as a slatted platform (or a supportive floor-sleeping setup designed for airflow) to let the underside breathe.
3. Ventilate hard for the first 48–72 hours:
   • Open windows if weather allows
   • Run a fan to move air across the surface
4. If humidity is high, use a dehumidifier in the room.
5. Delay installing a waterproof protector for a couple days if you can; protectors can trap odor during the highest-release window. When you’re ready, choose a breathable option from our protective layers.
6. Rotate or gently reposition the mattress after a day to let different surfaces breathe.

If you sleep closer to the floor (with or without a bed frame), these two resources go deeper on ventilation strategy: airflow tips for floor sleepers and how to reduce moisture buildup. For extra setup help, see our sleep accessories.

For tatami mats

• Air the mat in a dry, ventilated area.
• Keep it off cold floors and away from damp walls.
• If the room is humid, use a dehumidifier and ensure airflow on both sides when possible.

Why lumpiness after unboxing is common (and usually temporary)

Compression can create:

• Ripples from rolling
• Slight “steps” where layers were folded
• Temporary unevenness in quilted surfaces

Most of this improves within 48–72 hours as fibers relax and layers settle. Some mattresses benefit from light use, which helps the materials conform and distribute loft evenly.

If the product still looks unusually uneven after several days, that’s a good moment for a support check. But on day one, it’s generally part of the normal settling process.

FAQs

How long should a natural mattress smell last?

Most customers notice the biggest improvement within 48–72 hours with good airflow. For sensitive sleepers or latex/foam layers, 2–3 weeks is a realistic “best results” window.

Is this “off-gassing”?

Sometimes. With natural fiber mattresses, the more common cause is concentrated natural fiber aroma plus trapped packaging air and humidity. If foam or latex is included, those layers can contribute more traditional “new product” smell.

Why does it smell worse at night or in winter?

Closed windows, lower ventilation, and higher indoor humidity can make odors feel stronger. Odor molecules linger longer when air exchange is limited.

Does borate or borax smell?

Borate salts are generally considered odorless. If a product has a strong odor, it’s more likely from natural fibers, latex/foam, packaging concentration, or moisture exposure rather than borate itself.

My tatami mat smells like mold. Is that normal?

A mild grassy tatami aroma is normal. A strong moldy or “rotting plant” smell is not something to ignore. Increase drying and airflow immediately, and if it doesn’t improve quickly or you see any discoloration, contact support.

Can I put a mattress protector on right away?

You can, but if smell is a concern, it’s often better to air out first for a day or two. Waterproof protectors can trap odors during the strongest release window.

What can I do if the smell hasn’t improved after a week?

Try a more aggressive airflow setup: windows (when possible), a fan, and a dehumidifier. Ensure the mattress is on slats with airflow underneath. If the odor is musty/mildew-like or worsening, reach out to support.

Will the mattress feel different after break-in?

Yes. Natural fibers and layered builds often settle and become more consistent after the first couple weeks. This is normal, especially after compressed shipping.