Where you leave a cosmetic and how you close it affect how well it keeps. These are habits that take seconds.
Away from sun and heat
A sunny windowsill or a hot car is not a good place for cosmetics. The FDA explains that heat, temperature changes and exposure to light and air can change their characteristics. If the shelf that looks best in a photo gets sun for part of the day, the bottle is better somewhere else. Where a product states its own storage conditions, follow those.
Clean hands, a closed container
Washing your hands before use and keeping containers clean and tightly closed are among the FDA's general recommendations. When you finish, close the bottle properly and put it back in its place.
Keep the details from the box
The box may carry information that doesn't fit on the bottle. Before you throw it away, take a photo or note the name, batch, directions and stated durability. Write down the day you open it too, so you know how long it has been in use.
If it changes, stop
If the colour or smell has changed, stop using it. That is one of the recommendations in the FDA's safe-use guidance. If in doubt, ask before applying it again.