Story highlights Levi Strauss CEO Chip Bergh says we shouldn't machine wash jeans

Bergh shared the advice at a recent conference

He said spot cleaning works, and he hasn't washed his jeans in a year

Levi Strauss CEO Chip Bergh has some unusual style advice for 501 fans: Step away from the washing machine.

The denim honcho shared the words of wisdom this week at Fortune's Brainstorm Green conference in Laguna Niguel, California.

"These jeans are maybe a year old and these have yet to see a washing machine," he said of the pair he wore during a chat onstage. "I know that sounds totally disgusting."

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He recommended spot cleaning jeans with a sponge or toothbrush and a bit of detergent, then air drying. He says you should very seldom machine wash.

"If you treat them right, they'll last a long, long time -- probably longer than most people's waistline."

He added that less washing equals greater environmental sustainability.

It's not new advice. Designer Tommy Hilfiger has made similar comments. And CNN's Anderson Cooper told style expert Stacy London two years ago that he washes his jeans very rarely.

Jeans aficionados may be accustomed to hearing some unusual tips on keeping their denim products fresh. Advice ranges from spot cleaning jeans and never washing them to freezing them to kill any germs.

Jolie Kerr , who writes a column called "Ask a Clean Person," says it depends on your lifestyle and hygiene preferences.

"The way you'd care for a pair of jeans that you wear for yardwork versus ones you'd wear out dancing should be different -- the function should dictate how you treat a pair of jeans."