Yves Saint Laurent's relaunch of its iconic Opium fragrance is causing confusion among fragrance fans.

The fashion brand was strikingly vague when it came to details concerning the new scent, Belle d'Opium, not even naming it until shortly before the launch event in New York on June 17.

It was also debated whether YSL was just relaunching the scent with an updated image or if there was an entirely new formula involved. When respected perfume blog, the Perfume Shrine, dug deeper, representatives just said that that "it is a new and updated, more modern version of the classic YSL fragrance."

Later, its editor clarified that, indeed, "reformulation was necessary due to [...] restrictions on spicy ingredients (eugenol and iso-eugenol) which were necessary in the creation of the carnation heart of the memorable modern classic from 1977."

What that means is: if you're a fan of the fragrance, get shopping now, because the new version of it - to be launched this fall - will lack its characteristic spicy heart.

Fortunately for the brand, however, Belle d'Opium seems to be aiming at a much younger audience that won't remember the original scent, if the celebrities on hand to fete the relaunch are any indication: they ranged from TV host Alexa Chung to young media mogul Ashley Olsen and singer M.I.A - in short, the "who's who" of it girl fame.

One of them, upcoming French actress Melanie Thierry - who wasn't born when the fragrance first came out in 1977 - will star in the new ad campaign for the fragrance. And a new site (and YouTube channel), called What is Your Opium, which is updated daily with videos and 'fun facts' about the fragrance, will further contribute to reach out to that new audience.

To listen to perfumer Honorine Blanc talk about her inspirations for Belle d'Opium, click here: http://www.youtube.com/watch?v=gjSIHjoVYQU.

For impressions from the New York launch party, visit the following link: http://www.youtube.com/watch?v=e7ivY85i7ow.

According to the influential fashion blog Styleite, Opium's relaunch - together with Balmain's upholstery prints for fall, flared jeans or gap-toothed models like Georgia May Jagger - is one of the indications that the 1970s will soon celebrate a fulminant revival.