How to choose the right sunscreen

Dr Zainab Laftah, consultant dermatologist and British Skin Foundation spokesperson, explains how to pick the right sunscreen to best protect you from the sun's harsh rays.

Not just a burn

Sunburn can be painful, and cause skin irritation, peeling and even blistering in extreme circumstances. But it can also cause more severe damage. Excessive sun exposure and sunburn can lead to skin cancer.

Skin cancer is one of the most common cancers in the world. In the UK, more than 100,000 new cases of non-melanoma skin cancer are diagnosed each year. It affects more men than women and is more common in older people. Look out for:

• A small, shiny pink, red or pearly-white lump that grows slowly.

• Scaly, raised red patches that don't go away.

• A sore or ulcer that doesn't heal.

• A pink growth with raised edges and a dip like a crater in the middle.

• A growth with small blood vessels, like red wiggly cotton threads, on the surface.

Around 13,500 new cases of melanoma, the deadlier type of skin cancer, are diagnosed each year.

The most common symptoms to look out for include:

• Changes in the shape, colour, size and edges of a mole.

• Irregular colour across the mole, irregular edges or blurred, ragged edges to a mole.

• The formation of a new mole.

• A mole on the skin that keeps bleeding.

Skin cancer can occur anywhere on the body, with most cases diagnosed in people under 50. Some 2,000 people die from melanoma each year in the UK.

If you're worried about a mole, particularly changes with any of the signs above, you should speak with your GP as soon as possible.

Choosing a sunscreen

The sun's UV rays are so damaging that you should be wearing sun protection even when it's cloudy. Have we convinced you to wear sunscreen yet?

When choosing a sunscreen you need to look for two things:

1. Does it protect against UVA and UVB rays?

2. What is the sun protection factor (SPF)?

"Choosing a sunscreen is largely down to personal choice. Sunscreens are divided into mineral and chemical sunscreens, depending on their mode of action and the chemicals they contain," Dr Laftah says.

UVA and UVB

"The sun emits two wavelengths of light that penetrate the earth's atmosphere: ultraviolet A and ultraviolet B. Sunscreens are rated on their level of UVA and UVB protection. A broad-spectrum sunscreen with UVB and UVA protection is recommended," Dr Laftah explains. Because UV rays damage the skin in different ways, a sunscreen which only protects you from one type or the other isn't going to give you full protection.

"UVA rays have longer wavelengths at lower energy levels. They penetrate deeper into the skin, damaging the collagen and leading to the formation of wrinkles and skin ageing. UVB rays are shorter wavelengths with higher energy. They damage the DNA in the outer layer of the skin and excess exposure increases the risk of skin cancers developing."

Every time your skin gets damaged by the sun it can cause mutations in your cells, which can lead to malignant tumours. That's why it's so important you ensure you're protected from both forms of UV rays.

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What about SPF?

If you're one of those people who thinks one application of SPF15 is enough for an entire day outside, it's time to rethink. SPF15 is the lowest SPF recommended by doctors and so offers the least protection.

The longer you're in the sun, the more you need to apply sunscreen - it's recommended you reapply every two hours, or after swimming or heavy exercise.

On top of the SPF rating, you should also look for the 'star rating'. This reflects how well it protects against UVA rays compared to UVB.

"The SPF rating indicates the level of ultraviolet B (UVB) protection and is rated on a scale from 2 to 50+, whilst the star rating refers to the ultraviolet A (UVA) protection with a scale from 1 to 5," Dr Laftah says.

A rating of one star suggests the sunscreen doesn't protect well from UVA rays, so it's best to find one that has a 5-star rating. And as for SPF, 30 plus is best.

Do be aware, though, that a low SPF sunscreen with a high star rating will not provide as much UVA protection as a high SPF sunscreen with the same star rating. That's because it's dependent on the ratio of UVA and UVB protection. Just another reason for picking a higher SPF product.

"The SPF curve reflects the percentage of UVB blocked as the SPF rating increases; however, it is not linear and starts to plateau after 30," Dr Laftah explains.

"An SPF of 15 confers a protection of 93%, then 97% with SPF 30 and 98% with SPF 50. Therefore, the recommendation is application of SPF of 30+, 30 minutes prior to going outside, with reapplication every 2 hours or immediately after sweating or swimming to help reduce the risk of sunburn. UVA penetrates clouds and glass, thus a 4-star or 5-star rating for optimum protection is advised."

Can people with darker skin skip SPF?

Your skin colour can play a role in your natural sun protection, Dr Laftah says, but it doesn't mean you can skip sunscreen when spending time in the sun.

"Although individuals with darker skin colour have greater natural protection, skin cancers can still arise, and similar precautions should be taken.

"Research suggests that black skin has a natural SPF of 13.4 in comparison to 3.4 seen with white skin. Therefore, a sunscreen with an SPF of 15-30 may be sufficient for those with darker skin."

It's a date

Use-by dates aren't just for food, they apply to sunscreen too. That's because the minerals or chemicals in the sunscreen have a life limit on how long they're likely to protect you for.

"Expired sunscreens are less likely to provide adequate protection and the risk of sunburn is higher. They may also lead to skin irritation," Dr Laftah adds.

Check the label

Now you know all the things you need to look for in a sunscreen, you might be interested to know about the ingredients used in the creams.

Sunscreens are categorised into mineral and chemical creams, Dr Laftah explains.

"The mineral (physical) sunscreens contain titanium dioxide and zinc oxide, which block the UV rays from penetrating the skin by deflecting and scattering them like tiny mirrors," she adds.

"They tend to leave a white cast which can reduce their appeal; however, they are less likely to cause irritation to the skin and may be preferred for those with sensitive skin - for example, eczema and rosacea.

"Chemical sunscreens contain ingredients such as oxybenzone, avobenzone, octinoxate, octocrylene, octisalate, and homosalate, which are absorbed by the skin.

"They reduce UV damage by absorbing UV rays, converting them into heat before releasing this heat from the skin. They do not leave a white cast and are therefore favoured for darker skin types. They also have a lighter consistency and are preferred for oily and blemish-prone skin."