The short version: On US labels, rayon and viscose are two accepted names for the same fiber family. Lyocell is a permitted name for rayon made by one specific process, and modal is an international name the FTC accepts. A tag reading rayon made from bamboo is still describing rayon. A fiber label tells you what a garment is made of, where it was made and who stands behind it. It doesn't tell you how the fabric will perform.
Sleepwear tags might say rayon, viscose, lyocell or modal. They read like four different materials, but under US labeling rules three of them belong to one fiber family, and the fourth is an accepted international name. Here's how to read them, using the Federal Trade Commission's (FTC) guidance and the federal regulation behind it, linked throughout.
What a US fiber label must show
Fiber labels on US clothing follow the Textile Fiber Products Identification Act and the FTC's rules under it, with a separate law for wool products. The FTC's business guide, Threading Your Way Through the Labeling Requirements (FTC), lists the core items:
- Fiber content. Fibers by their generic names, with percentages by weight, from the largest share to the smallest. Very small amounts have a special rule, covered below.
- Country of origin. An imported item must name the country where it was processed or made.
- Who is responsible. Either the company's name or its Registered Identification Number (RN).
- English. Other languages can appear too, as long as the English version is there.
Washing instructions aren't on this list. They come under a different FTC rule, the Care Labeling Rule, and our guide to washing rayon and rayon-spandex explains what those label words mean.
Online listings have their own rules
Online and mail-order product descriptions must say whether an item was made in the USA, imported, or both. And if a written ad, online ones included, makes a statement about a fiber or implies one is present, it has to carry the label's fiber information, minus the percentages (FTC textile labeling guide).
Rayon vs. viscose: two names for one fiber family
What is rayon?
The federal regulation on generic fiber names defines rayon as a manufactured fiber made of regenerated cellulose (16 CFR 303.7(d), eCFR). The FTC notes that different plants, bamboo among them, can be used as a source for rayon (FTC bamboo guidance). Even so, rayon sits in the regulation's list of manufactured fibers.
What is viscose?
The same regulation also adopts the generic names in the international standard ISO 2076 (16 CFR 303.7, eCFR). The FTC explains that the ISO standard calls the predominant form of rayon viscose, and that a label may use either name (FTC textile labeling guide).
So on a US label, rayon vs. viscose isn't a choice between two materials. They're two accepted names for one fiber family. Neither name describes the fabric itself: its knit, weight or finish.
Where lyocell and modal fit
Lyocell sits inside the rayon definition. When the fiber is cellulose solidified out of an organic solution, with no chemical intermediates formed and no chemical substitution on the cellulose, the regulation allows the name lyocell (16 CFR 303.7(d), eCFR). The FTC's list of generic names shows lyocell under rayon (FTC textile labeling guide).
Modal comes in through the international list. The FTC's guide includes it in an appendix of ISO names that are permitted on US labels even though they aren't listed in the FTC's own rules (FTC textile labeling guide).
Lyocell vs. modal on a label
These sources don't describe how modal is made or how it compares with lyocell or viscose, so we won't guess. The label tells you which name the maker used. For anything more, ask the brand for its fiber documentation.
What "made from bamboo" means on a label
Bamboo is one of several plants that can be used as source material for rayon. The FTC has told sellers that most textiles marketed as bamboo, if not all, are actually rayon (FTC, How to Avoid Bamboozling Your Customers).
So the label should use the fiber's generic name, such as rayon made from bamboo or simply rayon. A product can be called bamboo only if it's made directly from bamboo fiber, and the seller needs reliable evidence, such as tests, that it is (FTC bamboo guidance).
The FTC's explanation: there's "no trace of the original plant" in finished rayon (FTC bamboo guidance). The words "made from bamboo" tell you where the cellulose came from. On their own, they don't say the fabric kept any property of the plant, and the FTC says a claim that it did needs proof like any other claim.
Bamboo viscose vs. rayon
Some listings say bamboo viscose. Since viscose is the ISO name for the predominant form of rayon, a fiber described as viscose made from bamboo is the same kind of fiber as rayon made from bamboo, written with the other accepted name.
Spandex and elastane
Under 16 CFR 303.7(k), spandex is a manufactured fiber made from a long-chain synthetic polymer that is at least 85% segmented polyurethane (16 CFR 303.7, eCFR). The ISO standard calls it elastane, and the FTC says a label may use either name (FTC textile labeling guide).
Small amounts follow a special rule. A fiber under 5% of the weight is generally listed as other fiber, not by name. The exception is a fiber with a definite function at that amount, and the FTC's example is spandex used for elasticity. Then the label may name it with its percentage. The FTC's sample label reads 96% acetate, 4% spandex, and a rayon blend follows the same pattern. The function doesn't have to be stated, only to exist (FTC textile labeling guide).
Trademark fiber names
Some fibers are sold under brand names. The FTC allows a fiber trademark on a content label only next to the generic name, in lettering of the same size and equal prominence. When a trademark appears on a label, the full fiber content has to be disclosed the first time it's used. Ads that use a fiber trademark, online ones included, must disclose the fiber content at least once, though not the percentages (FTC textile labeling guide).
For shoppers, the takeaway is simple: a fiber brand name shouldn't stand alone. Look for the generic name beside it.
What a label can't tell you
Breathable, cooling, soft and similar words aren't generic fiber names, and none of them appears in the regulation's list (16 CFR 303.7, eCFR). They describe how a finished product performs or feels, and a fiber name on its own doesn't establish them.
The FTC tells sellers they need substantiation for every claim they make, express or implied. In its bamboo guidance, that means competent and reliable evidence, such as scientific tests and analyses, and relying on other people's claims doesn't count (FTC bamboo guidance).
So if a listing calls a fabric breathable or cooling, it's fair to ask what supports it: which test method, which lab and which fabric. Rayon, viscose, lyocell and modal tell you what a fiber is, not how a garment will perform.
A 30-second label checklist
- Read the fiber line first. Generic names with percentages by weight, largest share first.
- Rayon or viscose? The same fiber family under US rules. Either name is allowed.
- Lyocell? A permitted name for rayon made by a specific solvent process.
- Modal? An ISO name the FTC permits on labels.
- Bamboo? Expect rayon made from bamboo, or simply rayon or viscose, unless the seller can show it's bamboo fiber itself.
- Spandex or elastane? The same fiber. Below 5%, it's named only when it has a function, such as elasticity.
- A fiber trademark? The generic name should sit right beside it, in the same size type.
- Origin. Imported items name the country. Online listings should say made in USA, imported, or both.
- Who stands behind it. A company name or an RN.
- Performance words. Breathable, cooling and similar terms aren't fiber names, so ask for the test.
This article is general information, not medical advice. Talk with your healthcare provider about symptoms and treatment options.
Sources (accessed 2026-10-17)
- 16 CFR 303.7, Generic names and definitions for manufactured fibers. Electronic Code of Federal Regulations (eCFR), Title 16 current as of 2026-10-15.
- Threading Your Way Through the Labeling Requirements Under the Textile and Wool Acts. Federal Trade Commission; edited October 2020 and January 2025.
- How to Avoid Bamboozling Your Customers. Federal Trade Commission, August 2009.
Each product page notes that the item is imported. Most product pages also show fiber content as listed by our supplier. We add the country where it was made once we've confirmed it from the sewn-in label.