Storing Essential Oils: Heat, Light, Air and Shelf Life
Why your oils oxidise, how to tell it has happened, and what shelf life actually means once the bottle is open.
Three enemies: heat, light, air
Essential oils are volatile and some are oxidation-prone. Heat speeds up degradation, light breaks down molecules, and air does the same work faster. A cool, dark, closed bottle is all the protection you need.
What the shelf life actually means
24-36 months unopened is the realistic window for a well-made oil in a dark bottle. Once opened, count twelve months. A 5 ml or 10 ml bottle that you use occasionally will outlast the oil in a 100 ml bottle you open every day, because headspace and repeated air exchange matter more than volume.
Spotting oxidation
Change of colour - a fresh citrus oil going from pale yellow to dark amber, or a pale oil turning brown - is the clearest sign. A flat, stale, slightly earthy smell is the second. Neither is dangerous, but both mean the material is no longer performing and should be replaced.
Refrigeration is optional
Fridge storage slows degradation but introduces condensation risk every time the bottle comes out. For most households a closed cabinet away from the cooker and out of direct sunlight is enough.
Store away from the things you use every day
A shelf above a radiator, next to a window or inside a hot car is the worst possible location. The best spot in a house is usually a bedroom or wardrobe cupboard, which stays cool and dark all year.