How to Store Natural Oils (and How to Tell If They've Gone Rancid)

Natural oils don't last forever. Over time they react with oxygen, a process called oxidation, and eventually go rancid. Rancid oil smells unpleasant, loses its softening qualities, and isn't something you want on your skin. The good news: a few simple storage habits keep your oil fresh much longer.

Why oils go rancid

Plant oils are made of fatty acids. The more 'unsaturated' they are, the more easily they react with oxygen. Light and heat speed this reaction up dramatically. That's why richer, more unsaturated oils like walnut are more delicate than almond or apricot.

The three enemies: light, heat and air

• Light speeds up oxidation. That's why we use amber glass.
• Heat speeds it up even more. A hot bathroom shelf or a sunny windowsill is the worst place for oil.
• Air feeds oxidation. Always close the cap tightly, and don't leave the bottle open.

Where to store your oil

• In a cool, dark cupboard or drawer.
• Away from the stove, heaters, geysers and direct sunlight.
• In Pakistani summers, a cool room is best. Never leave oil in a parked car.
• Some people refrigerate oils in summer. This is fine; some oils turn cloudy in the cold but clear again at room temperature.

Keep it clean

• Don't let water get into the bottle; it can cause spoilage.
• Don't touch the dropper or rim with your fingers.
• If you decant oil into a smaller bottle, make sure it's clean and completely dry.

How long do oils last?

Always follow the period shown on the label after opening, usually shown as an open-jar symbol with a number of months. As a general guide, richer oils with more polyunsaturated fats (like walnut) are more delicate and are best used sooner than almond or apricot.

Signs an oil has gone rancid

• Smell: sharp, sour, bitter, or like crayons, old paint or stale nuts.
• Colour: noticeably darker than when you bought it.
• Texture: thicker or sticky.
• Feel: it may sting or irritate skin that was fine with it before.

If in doubt, throw it out. Fresh oil should smell faint and pleasant.

Cloudy oil: is it spoiled?

Not necessarily. Many oils turn cloudy or thicken in cold weather or the fridge. Let the bottle return to room temperature; if it clears and smells fine, it's fine.

Homemade blends

If you mix your own oils, a blend lasts only as long as its most delicate oil. Make small batches and label them with the date. See DIY oil blends.

Hot weather? Read our tips for using face oil in summer. Choosing a new oil? See cold-pressed vs refined oil.