Dear Cecil: The CEO of Levi Strauss recently suggested jeans shouldn't be laundered, but left in the freezer overnight to kill bacteria and remove odors. Supposedly this preserves the fit and saves water. Previously, a student at the University of Alberta studied the growth of bacteria on his jeans after wearing them for months at a time, and concluded that the bacterial count eventually flatlines. He also put his jeans in the freezer to remove offensive smells. Will freezing my jeans get rid of their odor? Joe F., Berkeley

Cecil replies:

High time we got this sorted out.

At the Brainstorm Green sustainability conference in May that set the online world a-twittering about denim-washing best practices, Levi Strauss CEO Chip Bergh didn’t in fact suggest putting your jeans in the freezer. (At least he didn’t do so on camera.) What he said was you didn’t need to launder jeans, and claimed the year-old pair he was wearing had never seen a washing machine.

Bergh’s previous employer was soapmaker Procter & Gamble. One suspects there was bad blood.

Anyway, his green brainstorm: Life-cycle water consumption for a pair of jeans is more than 900 gallons. Much of this goes into pre-washing the denim at the factory; half is used by the customer washing the jeans at home. To save water, therefore, one might: (a) buy the new Levi’s line of factory-unwashed jeans, and/or (b) stop washing your jeans, other than spot-cleaning with a sponge or toothbrush and some detergent.

Freezing your jeans is another story. The idea has been floating around the Internet for a while, and evidently Levi’s spokespeople have blithely passed it along, but it wasn’t part of Bergh’s pitch in this instance. The Canadian undergrad you refer to, Josh Le, wore a pair of jeans for a year-plus without washing them, and claimed to have controlled their odor via freezing. But his project wasn’t conducted rigorously enough to support any claims about bacteria.

So let’s break down your question:

Q: Should you freeze jeans to kill bacteria and remove odors?

A: This advice is without scientific basis.

Q: Do you need to wash jeans?

A: I won’t say never. But you can probably wash them less often than most people do.

Personal testimony: Years ago, before the dawn of pre-washed denim, I maintained one might go a long spell between jeans washings, not so much to conserve water as to preserve jeans that had attained the optimal broken-in state between new-bought stiffness and eventual disintegration.

My jeans-care method was as follows:

1. Buy jeans. In the frontier days of my youth, while you did see some variety in jeans styles, for fabric you had one choice: new denim, which was a uniform blue and had the suppleness of plywood. You wanted to hustle through this phase as quickly as possible.

2. Wear jeans every day and wash them every night. I wasn’t one of those feckless adolescents who washed their jeans five times in a row or wore them wet to improve the fit. However, it was obvious machine washing accelerated the aging process, so I figured I might as well scoot things along.

3. The desired degree of fade and give having been achieved, sharply reduce the washing schedule, thereby postponing the day when the jeans get so threadbare you have to patch them, or (later) make cutoffs, or (finally) toss them and start over. I didn’t go a year between washings, and never tried the freezer treatment (frankly I’d never heard of the freezer treatment). However, assuming I didn’t spill 30-weight or something on my pants, I might go weeks or months between washings.

Then I met the future Mrs. Adams. She believed frequent if not daily washing of jeans (and everything else) was not merely a moral imperative but a practical necessity, because dirt itself, not agitation in the washing machine, was what accelerated fabric deterioration.

I had a choice: empirical observation or domestic harmony. I caved.

The facts remain:

Nobody claims you shouldn’t wash jeans if they become grimy or smelly. We assume, however, that the modern jeans-wearer leads a life of dirt-free, climate-controlled comfort.

Freezing jeans does nothing. It doesn’t kill bacteria, it just temporarily slows their growth. Heating jeans would do the trick, but is at odds with the goal of conserving resources.

As we’ve established here recently, the average person sheds a liter or more of insensible sweat per day. Much of this no doubt migrates through one’s clothes. However, the sweat emanating from most of the body’s surface is produced by eccrine glands, contains no oil, and doesn’t become smelly. The apocrine glands, which produce oily and potentially fragrant sweat, are concentrated in a few regions of the body, the relevant one for present purposes being the groin. Assumption number two: the modern jeans-wearer also wears underwear and changes it daily.

Washing jeans from the standpoint of odor suppression, therefore, isn’t urgent — and, to be blunt, blue hides the dirt.

No sense being an extremist, of course. My advice: wash those jeans annually, whether they need it or not.

Cecil Adams

Send questions to Cecil via cecil@straightdope.com.