All about sunscreen

Tips for sunscreen use:

• No sunscreen will completely shield you from the effects of ultraviolet radiation (UV). You can still burn, especially if you have sensitive skin
• Use additional forms of sun protection: avoid the sun around the middle of the day, wear a hat and clothing, wear sunglasses and stay in the shade if you can
• Using an SPF30+ rather than an SPF15 halves your risk of sunburn for the same length of time in the sun
• SPF30+ (or any sunscreen) should not be used to increase the amount of time you spend in the sun.
• Whatever the SPF, apply twenty minutes before going outside and reapply regularly, especially if swimming or sweating a lot.

How much protection?

The protection a sunscreen offers is affected by its sun protection factor (SPF) rating, how well and how thickly you apply it and how long is spent in the sun. It is also affected by skin type, when the sunscreen has been applied, the time of day, time of year and weather.

No matter how high the SPF rating, no sunscreen can block out all UV radiation. All sunscreens are filters allowing some UV through to the skin. The higher the SPF, the smaller the amount of UV that gets through. The longer the time spent in the sun, the more the UV accumulates until enough UV is present to cause sunburn.

Sunscreen's protectiveness is not affected by the length of time it has been on the skin, but it is affected by "wear and tear" over time. Even if you're not very active, sunscreen can rub off gradually and therefore needs to be reapplied regularly to top it up. This applies particularly to children.

Reduce sun exposure

UV accumulates and can damage the skin even when you're wearing a sunscreen and before burning is visible. Reduce your daily sun exposure as much as possible and in particular avoid the sun (even if using a sunscreen) between 11am - 4pm when UV is most intense. Sunscreens should not be used to increase the amount of time spent in the sun.

SPF

The SPF number shows how much protection is being offered. The higher the number, the more UV filtered and the greater the protection. Because of the number of factors involved, (eg time of the year, time of day, skin type) the SPF is not precise, but gives a general guide to sun protection.

SPF15 and 30+

An SPF15 sunscreen will protect from sunburn for approximately two-three hours, depending on skin type and how well it is applied. An SPF30+ rather than SPF15 halves the risk of sunburn for the same length of time in the sun.

The joint Australian/New Zealand sunscreen Standard, AS/NZS2604 has been revised so that the highest rating a sunscreen can claim is now SPF30+, rather than SPF15.

Broad spectrum

A broad spectrum sunscreen gives extra protection because it screens out most of the UVA radiation as well as UVB.

Water resistance

A water resistance claim of two hours means the sunscreen should retain its full SPF protection even after two hours in the water. However, even water resistant sunscreen should be reapplied after any water sports.

Applying sunscreen

Apply sunscreen 15-20 minutes before sun exposure to allow it time to dry and be absorbed into the skin. Spread it on to exposed skin thickly and evenly. If it's put on too thinly the protection is lessened and it won't work as well.

Reapplying sunscreen

Sunscreens need reapplying to remain protective. However, reapplying sunscreen does not reduce UV already received. It slows down further UV accumulation and if burning has already occurred, it may only further lessen the severity of burning. Reapply sunscreen every hour or more if you are swimming or sweating a lot.

Related topics

What is melanoma? See Melanoma

When you should consult a doctor about sunburn? See Sunburn

What other sun protection should I use? See Sun - clothing and hats

Original material provided by the Cancer Society of New Zealand. Edited by everybody.