Everything you need to know about sunscreen

Your sunscreen’s SPF (Sun Protection Factor) measures how well it protects your skin from sunburn. Sunsmart NZ recommends applying a broad spectrum, water-resistant SPF30+ sunscreen at least 20 minutes before sun exposure and then every two hours. Oh, and don’t forget you’ll still need to be sunsafe on those overcast days too.

The SPF is usually the first thing you look at when you buy sunscreen, but what else should you be looking for?

Buying a water-resistant sunscreen means you’re better protected when swimming, exercising or sweating. It’s important to note the word ‘resistant’ here – it’s not saying ‘waterproof’, so these sunscreens will need to be reapplied to remain effective.

UVA and UVB both contribute to ageing skin and skin cancer. UVA affects the skin cells that lie deep within the surface of the skin, whereas UVB is responsible for damaging the cells on the surface of the skin, causing sunburn. Both types of radiation can cause long term damage and can contribute to the development of skin cancer. A broad spectrum sunscreen protects you from both. 

Absorbers (chemical) and reflectors (physical) refer to what’s happening to the UV rays. The ‘absorbers’ absorb the UV, and the ‘reflectors’ reflect it. There are pros and cons to both solution types, but the decision will mostly come down to which one suits you and your skin type better.

Keep in mind that if you find a formula that works for you, then you’re more likely to use it!

There’s no trick question here: just choose the one you like applying – and apply it liberally. The Cancer Society recommends using at least a teaspoon of sunscreen (about 5mLs) for each limb. As long as you cover your skin thoroughly, the choice of application is up to you.

However, many people find it easier to apply the right amount with a cream, as opposed to an aerosol spray.

This is a big factor. The most effective sunscreen is one you’ll actually wear – so make sure you’re a fan of the smell, consistency and feel of your chosen brand and style. 

You should wear sunscreen whenever the UV Index is three or above. You can check what time you should be wearing protection based on your region by using the Sun Protection Alert map on the Sunsmart NZ website. The UV Index can also be high throughout winter and especially if you’re around reflective surfaces, so if you’re a keen surfer or snowboarder, you need to be extra careful.

It’s a common misconception that the heat from the sun causes sunburn, and that this causes cancer, because you can often feel the heat from the sun and you can’t feel or see UV. But even on a cloudy day, UV radiation can harm your skin.

Check the UV index on the NIWA website, or download the free SunSmart app that not only shows you the index, but also indicates the times during the day you’ll need to be wearing protection. But really, it’s a good idea to get into the habit of applying sunscreen every day. 

Studies have shown that using sunscreen doesn’t stop you from topping up on Vitamin D – so apply it liberally.

While Vitamin D (also known as the ‘sunshine vitamin’) can be absorbed from a variety of food such as oily fish and milk products, sun exposure is the easiest way to maintain those levels. Depending on your skin type, a few minutes of incidental sun exposure a couple of times a week should be sufficient for most people but you will still need to remember to be sun safe.

If you’re concerned about your Vitamin D levels, you can bring this up with your GP about whether additional supplementation is appropriate. 

It’s a good idea to keep in mind that sunscreen can have a shelf life of anywhere between 6 months – 3 years depending on the product and whether it’s been stored correctly. So, give that bottle a quick check before application.

"A sunscreen that has expired should be discarded, as it is less effective at preventing damage from ultraviolet light... the SPF listed on the label is not guaranteed for expired products, be it chemical or physical sunscreen," says dermatologist Dr Meghan Feely.

Unlike Australia, New Zealand doesn’t have any mandatory standards for sunscreen, which means you really need to read the label and look into what different products offer, read reviews online and make a decision from there.