Does zinc oxide expire?

What if there is no expiry date?

In the United States, sunscreen can be sold without an expiry date when stability testing shows that the product stays stable for at least three years. For an undated bottle, count from purchase, not from the day you opened it. If you cannot establish how old the sunscreen is, discard it. Expired sunscreen might no longer be safe and effective.1

Can you tell by looking at it?

A change in color, consistency or smell is a reason to replace sunscreen. Do not wait for the three year mark if the product has changed. Checking its appearance is useful, but it is not a substitute for checking its age: the expiry date remains the cutoff even when the sunscreen looks familiar.2

Mineral sunscreen can naturally be thicker and harder to spread than chemical sunscreen, which gives a cream a surprising amount of administrative work. Zinc oxide sunscreen can also leave a white cast. Those usual characteristics are different from a change in how your particular bottle looks or feels.2

Does heat affect the shelf life?

An expiry date is not permission to expose sunscreen to extreme heat. Heat exposure can undermine the assumption that a bottle remains usable until its printed date. Replace old sunscreen that has been exposed to extreme heat rather than relying on the date alone.3

Keep sunscreen containers out of direct sunlight and excessive heat. Outdoors, keep the bottle in the shade or wrap it in a towel instead of leaving it in direct sun for long periods. Storage matters for maintaining the product's effectiveness, including before its expiry date.1

What should you replace it with?

Choose a broad spectrum sunscreen with SPF 30 or higher. Broad spectrum means protection against both UVA and UVB rays. Brand names matter less than broad spectrum protection and regular use, which gives the logo a fairly small job. Zinc oxide is a mineral sunscreen ingredient, and mineral formulas can be less irritating for sensitive skin.45

For swimming or heavy sweating, choose a water resistant formula and check its reapplication directions. Water resistance lasts for the period stated on the label, either 40 or 80 minutes during swimming or sweating. No sunscreen is waterproof, and a fresh bottle still needs reapplication.13

How to use the replacement bottle

1. 1Apply sunscreen before going outdoors. General sunscreen guidance is to apply it 15 to 30 minutes before sun exposure.
2. 2Cover all exposed skin generously. An adult needs about one ounce, enough to fill a shot glass, for exposed body areas.
3. 3Include easy to miss areas such as the ears, hairline, neck and tops of the feet.
4. 4Reapply at least every two hours outdoors, and after swimming or sweating, following the label's directions.