By Nick Antonovics

PARIS (Reuters) - Underwear that helps women slim or men feel cool and fresh -- purveyors of cosmeto-textiles were out in force at Paris's annual lingerie trade fair on Sunday.

But opinion was divided on whether high-tech fabrics encapsulating slimming agents, perfumes and creams would be a lasting addition to wardrobes or a passing fad.

"There are a lot of brands that have worked on the idea but there has never been a paradigm shift. What interests consumers in the end are fairly traditional products," said Hubert Lafont, chief executive of Barbara, a leading French lingerie firm.

Several companies have proved the technology works and can be a commercial success. Others have since abandoned production.

Philippe Andrieu began his company Onixxa in 2003 with just one product -- a pair of tights with a slimming agent in them. Now he has over 30 garments, including slimming jeans, under the Lytess trade mark, and annual sales of 4.5 million euros ($5.9 million).

He expects turnover to quadruple by 2009, and said the total market could be worth up to 500 million euros.

"Adidas is coming. Nike will follow and L'Oreal is interested," he said. "We have proved it works."

Canadian textiles giant Invista, part of privately held Koch Industries, launched its brand of cosmeto-textiles under the Lycra Body Care trademark two and a half years ago and now has clients around the world, including men and women's underwear makers and manufacturers of socks and tights.

The textiles -- containing aloe vera moisturizers, nutrients derived from seaweed or perfumes -- are promoted as making people feel fresh or cool or to help keep skin moist.

"This is all about well-being and emotions rather than providing therapeutic benefit," said Fiona Paul, an Invista spokeswoman.

LIMITED LIFE

Existing cosmeto-textiles contain microscopic capsules of cosmetics that break as the fabrics rub skin, releasing the active ingredients. Invista's capsules come from International Flavors and Fragrances, while Onixxa's are made by French group Robert Blondel SA.

The active life of any garment is limited to between 20 and 40 washes, depending on the ingredient, and -- so say sceptics -- this is the main drawback.

"We don't promote this product any more. It was our first trial," said Daisuke Utaka on the stand of La Cle International, a Japanese company that launched a line of panties containing a skin moisturiser derived from rice two years ago.

"We still believe the idea is good but ... I don't think consumers want this yet," he added.

Blondel chief executive Yann Balguerie expected perceptions to change in three years when European standard-setters have created common rules for the sector, which currently has to comply with both cosmetic industry and textile regulations.

As an interim solution, the French industry -- which is getting strong government support -- will this month launch a quality label to encourage take up of the technology, he said.

Already others have gone further. An Italian company, BioFarm, was promoting a textile comprising nano-particles of silver that kills bacteria on skin, among other properties.

"The difference between this material and micro-capsules is that it lasts for life and doesn't release any active substance," said Marketing Adviser Moreno Cremaschi.