“Sunscreens have differing expiration timescales after opening, depending on the product or brand,” explains Dr Du-Harpur. While most sunscreens last around the 12-month mark, some have been tested for stability for a little longer – around 18 months or two years. “It’s important to check the packaging for a logo that looks like a pot with a timeframe on it and I wouldn’t recommend using it after this time.” 12M means it’s good for a year, 24M means it’s good for two years, and so on.

It’s also important to note that where you store your suncream has a massive affect on its stability. “Incorrect storage in extremes of temperature, particularly heat, can also destabilise a product faster than anticipated.” So if you’ve had that bottle of suncream lying in direct sunlight on the beach (and haven’t we all), chances are it won’t last as long.

“How bad is it to use sunscreen that’s over a year old, and how do I tell?”