“We worked with perfumers to achieve an identical perfume, replacing one molecule with a fresh floral note for an equivalent one that gives this transparent floral effect,” says Anaïs Paillard, fragrance development coordinator at the company. “We also reduced a couple of ingredients with citrus notes and another with an aromatic note with a lavender effect. We worked to balance the formula using equivalent substitutes.”

— On Halloween Eau de Toilette, which has been reformulated twice. Read more in Why doesn’t my favorite perfume smell the same anymore? The mysterious task of fragrance reformulation at El País.

Reformulation is much more difficult than it seems, to the point of becoming an integral part of the perfumer’s job. We are often asked to alter a fragrance slightly, make a fragrance more floral, more diffusive, creamier. In the case of reformulation, we have to do the same thing. We have to change the fragrance without really changing it, without losing its character, because some consumers have been buying a perfume for such a long that they know it by heart. So the challenge is to figure out how to change without changing.

— Read more in Olfactory reformulation a delicate exercise at Premium Beauty News.