Anyone using sun cream in heatwave urged to check three-digit code

Temperatures in the UK are set to climb into the 30s this weekend as the heatwave brings hot and dry conditions across the country. The Met Office says temperatures will peak on Saturday, July 12, reaching highs of 33C in some parts of England and Wales, and the warm weather should continue into Sunday, before cooling slighty next week. But it means shorts and t-shirt weather is very much here for the weekend and while it's a great time to spend time outdoors and soak up some rays, it's important to be mindful of sun exposure over the coming days.

Being out in the sun increases the amount of UV radiation we're exposed to, which can be damaging for both the skin and eyes. UV rays are typically strongest between 10am and 4pm and UV radiation is highest during the summer, but you can still be exposed even when it's cloudy so stay well protected by wearing sunglasses and plenty of sun creamis key.

The NHS recommends using a sun cream with a sun protection factor (SPF) of at least 30 to protect against ultraviolet B radiation (UVB), and with at least four-star ultraviolet A radiation (UVA) protection. You should see a star rating of up to five stars on bottles of suncream and the letters "UVA" will be labelled inside a circle. This is a European marking and means the UVA protection is at least a third of the SPF value and meets EU recommendations.

But there's another important symbol on bottles of sun cream that you need to check before applying and that refers to the expiry date. There should be a small symbol on the back of sun cream bottles that looks like an open jar and this will have a three-digit code inside it.

The code is made up of two numbers and a letter, such as '12M' or '18M', and this indicates that your suncream is safe to use for 12 or 18 months after opening. If your sun cream has been open for longer than this number then the product will no longer be effective and won't give you the required level of protection you need.

Benenden Health explains: "To know when suncream expires, all you need to do is look out for the symbol that looks like an open jar on the sunscreen bottle. This has a number inside that tells you how long the product should be used after it has been opened.

"For example, if you see '12M' in the open jar, then the sun cream should be used within 12 months of cracking it open. After that time, the sun cream becomes ineffective - no matter how high the sun protection factor is. As such, try to remember when you last opened it and, if you know you used it last year, it's time to buy a fresh one."

Most sun creams have a shelf life of around three years, but if the bottle has already been opened then you need to make sure you use it within the timeframe specified on the symbol on the bottle, which will usually be 12M (12 months).

Susanna Daniels, CEO of charity Melanoma Focus, adds: "In the UK, on sun lotion bottles you'll see an SPF - you're looking for anything above SPF 30 - and there'll be a star-rating usually on the back. You're looking for a four or five star rating, which equates to your UVA protection.

"There's also a picture of a bottle being opened, and it might have '12M' on it - that indicates how long the sun lotion will last before it expires. 12M means it will expire after 12 months of opening the sunscreen. Anything that's kept in light or heats up, might not last as long as that."