Reformulation
A change to an existing perfume’s formula. It is separate from a new flanker, a change of packaging or variation between production batches.
Reformulation means changing the composition of an existing fragrance. A change might concern the materials used or their proportions. The word identifies a formula change; judging whether you prefer the result requires comparing the actual versions.
Ingredient requirements can be one reason. Papillon’s FAQ explains that a change in permitted material levels could require an adjustment, while stating that it would notify customers and stockists if it had to reformulate. That is one house’s account, rather than evidence that every brand makes or conceals the same changes.
Packaging can change separately. Escentric Molecules says in its packaging FAQ that its redesign left its fragrance formulas unchanged. A different bottle or box therefore gives you a question to check with the maker, rather than proof of a new formula.
If an older sample matters to your purchase, note its full name, concentration and any available batch details, then compare it with a current sample. Describe the difference you notice, such as a sweeter opening or quieter drydown. Keep that observation separate from an explanation the maker has confirmed.