I'm an anti-aging expert and you should always pay attention to a key symbol on your sun cream to avoid getting burnt

Liz Wadden has over 78,800 TikTok followers for her 'face yoga' techniques Read More: Hairdressers issue warning against 'hair dusting' TikTok trend which promises to banish split ends 

An anti-aging expert has warned people of the dangers of not paying attention to their sun cream's expiration date.

Liz Wadden, from Nova Scotia, went viral on TikTok earlier this week when she urged her 78,800 followers to take note of the symbol on the back of their suncream bottles.

The social media star - who shares her 'face yoga' techniques for looking young - reminded her audience to take note of the expiration date on back of their sun cream bottles when they first open it.

Typically, sun creams can be used for up to a year after they've been opened - but their effectiveness varies from brand to brand.

Usually, the bottle will feature an illustration of a pot with the lid off and '6M', '12M' or '24M' written next to it - indicating how long it will last.

Liz Wadden, from Nova Scotia, went viral on TikTok earlier this week when she urged her 78,800 followers to take note of the symbol on the back of their suncream bottles. Stock image

Liz said in her TikTok caption: 'Over time, the active ingredients in sunscreen can break down, making it less effective at protecting your skin from harmful UV rays.'

She then went on to note how the consistency can change over time and render the product less effective too.

Liz added: 'Expired sunscreen can change in texture, becoming clumpy or runny, which means it won't apply evenly on your skin.'

Thirdly, the expert highlighted how out-of-date sun cream can also cause skin irritation and urged her followers to be 'better safe than sorry'.

Finally, Liz reminded followers of the optimum sun cream storage conditions too.

She continued: 'Heat and sunlight can accelerate the breakdown of sunscreen ingredients, so even if it's not expired, improper storage can reduce its effectiveness.'

It comes as Dr Elizabeth Blakeway-Manning, a consultant dermatologist in Yorkshire and the Melanoma Fund's medical ambassador, shared her top tips for staying safe outdoors with MailOnline.

Cancer Research UK says rates of skin cancer have more than doubled since the 1990s, and sun exposure is the culprit in nine out of 10 cases.

Dr Elizabeth Blakeway-Manning, a consultant dermatologist in Yorkshire and the Melanoma Fund's medical ambassador, shared her top tips for staying safe outdoors with MailOnline

There are two broad groups of skin cancer - melanoma, which arises from the pigment producing cells in the skin, known as melanocytes, and non-melanoma skin cancer, which predominantly arises from the keratinocytes, the major cell type in the epidermis or top layer of skin..

Melanoma is the far more deadly type - accounting for almost three times the number of non-melanoma deaths each year.

In total, more than 3,000 people will die from skin cancer each year in the UK, while almost 10,000 people will lose their lives to the disease annually in the US.

Too much UV radiation from the sun or sunbeds can damage the DNA in skin cells, which can cause them to start growing out of control and lead to skin cancer.

Exposure to UV rays can also cause early ageing of the skin, including wrinkles, age spots and sagging, according to skin cancer charity the Melanoma Fund.

But while sun screen is vital for UV protection, there are other ways to help shield your skin from the rays.

Clothing is key protection 

Your first line of defence should be clothing — and you should make sure to apply sunscreen to all exposed areas.

Clothing absorbs or blocks harmful UV rays

But as the day heats up, it's a 'natural impulse to remove clothing', the experts said.

This can mean leave skin exposed, making it key to apply cream to these areas.

Dr Blakeway-Manning, who is also a consultant dermatologist at Harrogate and District NHS Foundation Trust, also recommends always wearing a hat — such as one with a legionnaire flap at the back or a wide brim.

This is because your forehead, scalp and ears are particularly vulnerable.

Shade protects from UV rays

For those less adoring of the heat, the shade offers a welcome reprieve.

But it's also a good way to give your skin a break from powerful UV rays.

The experts say that, along with clothing, shade is the best UV protection.

If shade is hard to come by, they recommend using temporary structures such as gazebos, sails, or sports umbrellas.

Best sunscreen is broad spectrum SPF30+ non-greasy

A broad spectrum sunscreen will protect you against both types of harmful ultraviolet (UV) rays (UVA and UVB).

'As a parent, lead by example and apply to your skin as well as theirs,' says Melanoma Fund's CEO Michelle Baker.

You should apply sunscreen 20 minutes before heading outdoors to ensure it has time to set and dry. This also prevents it from running off into your eyes when you start to sweat.

It's also key to pay special attention to your ears and nose – areas many people forget.

'If using technical protective equipment, be sure to apply a non-greasy sunscreen formulation in advance to avoid the product compromising effectiveness,' the experts added.

Check your sunscreen is in date 

Sunscreens have a shelf life.

The expiry date is marked on the outside of the container, however moisture, high temperatures, direct sunlight and potential contamination might hasten degradation so try to use newly purchased sunscreen each year.

Writing the first date of use on the bottle to remind yourself how long it has been open for is recommended.

Always re-apply, even once-a-day sunscreens  

Reapplication of all types of sunscreens is recommended every two hours, even for once-a-day formulas.

The experts claimed this is because no matter how diligently you apply, parts of the body will likely be missed — which could leave particular areas of skin vulnerable for the whole day.

Perspiration, water and wiping off dirt can all remove even a once-a-day product — especially if you are undertaking vigorous outdoor activities.

Wear light fabrics with a tight weave

Wearing light clothes that have a tight weave are best in the sun, said Dr Blakeway-Manning and Ms Baker.

Tightly woven fabrics will allow less UV rays to filter through.

Furthermore, many items of clothing, particularly sportswear intended to be worn outside have a labelled UV protection factor (UPF) so this is worth looking out for.

Don't get caught out by rays  

Many people get a sunburn from being caught out by the weather, the experts said.

Often, you can start an activity in the early morning when the weather is mild, but it then turns into a hot day. This can then result in sunburn, they claimed.

On top of that, it's possible to get a sunburn on overcast days. This is because clouds provide little protection against the UV rays.

To find out whether sun protection is needed that, check the UV index, which can be found on weather websites.

The experts recommend using sun protection if the UV is as little as 3 or above.  

Never use sunbeds 

Many people have a desire to tan their skin, whether that be through sunbeds or faking it.

But sunbeds, sunlamps and tanning booths give out high intensity UV light with the aim to produce a rapid tan — a tan is the skins reaction to damage from too much exposure to UV radiation. This can increase the risk of developing skin cancer.

Signs of skin damage are not always obvious for up to 20 years.

Skin cancer usually starts with a new or changing skin mark or mole, which may later scab or bleed.

Dr Blakeway-Manning and Ms Baker have stressed that there is no such thing as a healthy UV induced tan, instead 'fake it and never use sunbeds. It is also important to remember that fake tan does not protect you from UV rays and it is still important to protect yourself from the sun'.

Sun exposure is needed for vitamin D 

Despite the need to protect your skin from the rays, it can also offer some benefits.

We know that we make most of our vitamin D when our skin is exposed to the sun’s UV rays. Vitamin D plays an important role in bone health.

Vitamin D is made as the sun's ultraviolet B rays (UVB) interact with a pro-vitamin in the skin called 7-DHC.

This system is very efficient and relatively brief exposure will trigger vitamin D production. The amount of UV that an individual absorbs from the sun however depends upon biological, environmental and behavioural factors so when it comes to sun exposure and Vitamin D, one rule certainly does not fit all.

Individuals with skin cancer risk factors and / or a prior personal history of skin cancer would certainly be advised to prioritise reducing their UV exposure and supplement Vitamin D, particularly if Vitamin D levels are known to be insufficient.

In fact, NHS advice is that everyone should consider taking a daily supplement containing 10 micrograms of vitamin D during the autumn and winter.