It’s almost always down to oxidation from heat, light or air exposure over time, though old age, poor storage, or a change in your own skin chemistry can all play a part too.

What’s actually happening in the bottle

Perfume ingredients slowly break down when exposed to warmth, sunlight, and repeated opening lets in oxygen that speeds the process further. Citrus and other lighter top notes tend to go first, which is often what people describe as a fragrance turning ‘sour’ — the fresher elements have faded, leaving behind a duller, sometimes slightly rancid-smelling base. A bottle kept on a sunny windowsill or in a warm bathroom will degrade much faster than one kept in a cool, dark drawer.

What to check

  • How old is the bottle, and how has it been stored?
  • Has the colour darkened noticeably since you bought it?
  • Has anything changed with your skin, medication or diet, which can occasionally alter how a familiar scent reads on you?

If the bottle is still within a couple of years old and has been stored sensibly, a sudden change is more likely down to a skin or health factor on your end than the perfume itself having gone off.

Our guide to storing perfume correctly explains how to slow this process down, and our complete guide to perfume covers why some ingredients are more fragile than others.