We’ve all been there. The sun makes an appearance and the temperature rises. But you’re unprepared, thinking this summer was never going to happen, and haven’t stocked up on much-needed SPF. So what do you do?

You plough headfirst into your bathroom cabinet, of course, rummaging past long-forgotten bottles of mouthwash and shampoo. Finally, you emerge triumphant – a half-used bottle of sunscreen from last year’s holiday in hand — ready to slather it on and head outside. 

Not too fast. Your glory may well be misplaced. You see, as with all beauty products, sunscreen has an expiry date. You might turn a blind eye to a shower gel two weeks past its ‘period after opening’ (PAO) date, but when it comes to SPF there’s an important reason why you want to avoid using a formula past its best. 

To get the full story on the lifespan of our suncare, we spoke to Dr Marko Lens, the founder of Zelens skincare, 

Just like all other cosmetic products, sunscreen comes with a PAO date, which basically denotes how many months the product will stay ‘good’ for after you first open it. This should be fairly easy to spot, most often appearing as a symbol that looks like the outline of a moisturiser tub with a number and the letter M inside. 12M means it’s good for a year, 24M means it’s good for two years, and so on.

As for SPF? “Usually the sunscreen should be valid for 36 months from the date of the production, if not opened. If opened, it’s usually valid for six to 12 months, but be sure to check the packaging,” explains Dr Lens.

It’s pretty simple. “Expired sunscreen does not provide protection and that is why it is bad to put it on your skin,” explains Dr Lens. It won’t necessarily have an adverse effect on the skin, but as the protective filters degrade over time, wearing old sunscreen has the same protection as wearing none at all.

As Dr Lens explains, the main thing that will cause a sunscreen to expire is the degradation of the sunscreen ingredients. However, it’s also recommended that you store sunscreen in a cool, dark place to prevent the acceleration of that degradation. Basically, don’t leave your bottle of SPF in full view of the sun.

Dr Lens admits that the only way to test just how useless an expired sunscreen is would be through a quantitative analysis. “However, smell and texture are also very important indicators of the stability of the formulation,” he adds. If you notice your SPF has changed texture, perhaps turning lumpy or a bit drier than usual, or if you notice the smell is a bit off, then it’s likely the sunscreen will no longer be effective.

The real thing to note here is that with proper use, you really shouldn’t ever have half-used bottles of sunscreen lying around at all. Dr Lens recommends: “One teaspoon for the face and neck, one for each upper arm, one for each leg, one for abdomen and chest and one for the back.” Once you factor in reapplication every two hours, you soon realise that you should be working your way through a bottle of sunscreen pretty quick.

Images: Getty