Sunscreen 101

As we head into summer in the southern hemisphere, it’s a good idea to remind ourselves about the principles of sunscreen. We should be wearing sunscreen all year round — as any sun exposure is potentially damaging — but this is especially true during our hot African summers. You may think that all sunscreen is created equal, but that’s not necessarily true. Here are some things you may not have known about sunscreen:

What is SPF?

SPF stands for sun protection factor, and to work out how high an SPF to use, you need to know roughly how quickly you burn in the sun without wearing any sunscreen. According to, you multiply that number — say 10 minutes — by the SPF stated on the bottle (SPF25, for example) to get the amount of time your skin will be protected. In this case, that’s 10 x 25 = 250 minutes. Divide that by 60 (the number of minutes in an hour), to get 4.16 hours, or just over four hours of protection.

Generally though, sunscreen should be reapplied every two hours, as sunscreen is eroded by exposure to water and sweat.

Difference between UVA and UVB

You might have noticed some mention of “UVA”, “UVB” and “broad spectrum” on sunscreen bottles, but what does that all mean? According to SkinCancer.Org (and without getting too scientific) UVA stands for ultraviolet A and UVB is ultraviolet B, and refers to two types or lengths of light waves emitted by the sun. For us, it’s easier to remember those as UVA for aging and UVB for burning, which is the immediate effect they have on our skin. SPF only refers to the protection provided against the UVB rays — the ones that burn — so it’s essential to ensure that your sunscreen is ‘broad spectrum’, protecting you from the burning rays, but also those that age the skin prematurely.

Commercial vs natural

Increasingly, we’re being advised to use mineral sunscreens over chemical ones. This means looking for these natural, mineral ingredients that help to protect and moisturise your skin without lathering it in chemicals. Look out for:

  • Zinc oxide: mineral UVA & UVB protection; can leave a whitish cast on skin
  • Titanium dioxide (non-nano): mineral UVA & UVB protection; unsafe if inhaled
  • Organic moisturising ingredients like aloe, coconut oil, calendula, etc.

How often should you replace your sunscreen?

Sunscreen is expensive, and if you still have a bottle floating around from last summer, it can be tempting to throw that into the beach bag and have done with it. But one last check you should do is for the expiration date on the bottle*. Sunscreen is tested under lab conditions to remain effective over time, and if yours has expired, you should replace it.

If it’s not already, applying sunscreen should become a part of the daily ritual of everyone, no matter your natural skin tone. The sooner you start protecting your skin, the lower the likelihood is that you’ll experience the harmful effects of sun exposure. Cape Town GP, Dr Jo Leach says “a child or adolescent suffering one or more bad sunburns more than doubles their chances of developing skin cancer later in life. Teaching children to have lifelong healthy skin habits — being sun-safe and preventative — is important.”


* Ask the expert: Does sunscreen become ineffective with age?:


  1. Calculate Your Recommended SPF:


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