A new Facebook craze is sweeping the social networking site, where woman give details of their bra colour, to help raise awareness for breast cancer.

Women have been giving details of their bra colour to help raise awareness for breast cancer on Facebook.

Thousands of female users – and some male ones – began updating their statuses on Friday with “beige”, “hot pink”, “crimson red”, “sexy black and gold” or even “nothing”.

As online confusion raged and dozens of bloggers speculated about its meaning, it was disclosed it was part of a new campaign to help raise awareness for breast cancer.

Within hours of the craze starting, dozens of Facebook groups began appearing, with one group “breast cancer awareness ♥ I updated my Status with my Bra colour ♥”, having more than 33,000 fans.

The most popular colours appeared to be “white,” “black” and “beige”.

One blogger wrote: “Women everywhere are setting the bra colour they’re wearing today as their Facebook status.

“The purpose is to promote breast cancer awareness, and remind women to get checked.

“The disease is very often curable if caught early enough.”

Another blog suggests the craze was started by women in Detroit, trying to raise awareness for the disease.

Andrea Rader, a spokeswoman for the Susan G. Komen for the Cure foundation, said the group was not behind the campaign.

She called it but called it “a terrific tool for raising awareness.”

She added, “We just hope people act on it — get educated, get a mammogram.”

Malorie Lucich, a spokeswoman for Facebook, said she was not sure where or how the craze started.

But she said it was an example of a “grass-roots” movement beginning on the social networking site.

“What is particularly unique about this grass-roots campaign is that it seems to have been started by a user or group of users, as opposed to an official entity, and spread virally throughout Facebook,” she told CNN.

“It’s an ideal example of how an individual voice can be magnified to create awareness for a good cause and ignite action among millions by using a site like Facebook.”