"The natural properties of the bamboo plant are simply not going to survive" the rayon-making process, adds Dr. Hardin, professor emeritus of textile science at the University of Georgia in Athens, Ga. Rayon is made from cellulose typically obtained from trees, but it can be obtained from bamboo, and the result is a virtually indistinguishable fabric, he says.
The Federal Trade Commission filed administrative complaints in 2009 against four companies selling products labeled as bamboo. According to the complaints, the companies' labeling and advertising was "deceptive" because the products weren't natural bamboo and didn't retain its antibacterial qualities. The cases were subsequently settled, and the companies agreed not to make false claims, according to court documents.
Dr. Hardin's study included Jonano brand products sold by Sami Designs LLC of Wexford, Pa., and Bamboosa brand products sold by M Group Inc., Andrews, S.C. Both companies were part of the FTC's 2009 settlement. Bonnie Siefers, owner of Sami Designs, declined to comment. A representative for M Group couldn't immediately be reached for comment.
In 2010, the FTC sent letters to 78 retailers warning them to stop advertising rayon products as bamboo. Last week, to settle an FTC complaint, four retailers—Amazon.com, Leon Max Inc., Macy's Inc. and Sears Roebuck & Co.—agreed to pay a total of $1.26 million in penalties, the agency said. The complaint said the companies violated federal textile-identification law by labeling products as bamboo without disclosing they were rayon. In the proposed agreement, the retailers didn't admit to wrongdoing. Macy's declined to comment; Amazon and Sears didn't return calls; and a representative for Leon Max couldn't be reached for comment.
A $48 yoga towel from Manduka LLC is made of polyester infused with "activated carbon" derived from recycled coconut shells. The Ombré eQua Plus towel, made from Cocona brand fabric, "provides superior odor management," according to the El Segundo, Calif., company's website. Manduka says its "internal focus group" found that after heavy use odor was "negligible" compared with a similar towel without the carbon.
Recycled coconut shells are used to make the carbon, which is embedded into polyester yarn to make Cocona brand fabric, says Chris Castagno, chief marketing officer of Cocona Inc. of Boulder, Colo. The carbon absorbs moisture. Cocona-funded studies have found the fabric dries faster than other materials and a dry fabric is less likely to grow bacteria, Mr. Castagno says. Cocona doesn't claim its fabric is antibacterial and doesn't have any studies to show it slows bacteria growth, he adds.
Eucalyptus sheets from Sacred Sleep LLC ($200 for a queen set) are "antimicrobial" and deter dust-mite growth, the Salida, Colo., company says. The fibers used in its sheets are called Tencel, made from eucalyptus trees by Austria's Lenzing AG. Sacred Sleep says its claims are based on studies by the manufacturer.
Tencel, a type of rayon made using an environmentally friendly process, is also used in towels, baby wipes and apparel. The fibers don't kill bacteria but their structure draws in moisture to create a "desert-like atmosphere" on the surface that is inhospitable to bacteria, says Nina Nadash, a home textile merchandiser for Lenzing in the Americas.
At least two published scientific studies have tested Tencel's ability to retard bacterial growth. A study published in 2009 in the Journal of Applied Microbiology put underarm sweat samples from five men and five women on a variety of fabrics, including cotton, polyester and fabric made from Tencel. The fabrics were incubated in a warm, wet environment for 24 hours. The Tencel fabric with male sweat showed less bacteria growth than most of the other fabrics but the results weren't statistically significant, meaning they could have occurred by chance, the study says. Tencel fabric grew fewer bacteria on the samples with female sweat than polyester, but about the same as cotton. Tencel fabric, however, was the best at discouraging odor-causing bacteria, says Bernard Redl, a microbiologist at Austria's Medical University of Innsbruck and a study author.
A 2009 laboratory test funded by Lenzing found that fabric with Tencel fibers deters dust mites. According to the test results—which were obtained from the website of Valley Forge Fabrics Inc., a Pompano Beach, Fla., company that sells Tencel sheets—swatches of a Tencel-cotton blend and a control fabric of 100% cotton were infected with 300 dust mites. After 42 days in the lab, the Tencel-cotton swatches had no dust mites while the controls had an average of 5,500 mites.
This type of study doesn't mean a sheet will help allergy sufferers, says Darryl C. Zeldin, scientific director of the National Institute of Environmental Health Sciences, as it wasn't done "in a real setting, when people are sleeping in their beds" and there would be moisture from human bodies and skin flakes, which mites eat.
Officials at Lenzing couldn't be reached for comment on the dust-mite study.