The 5 SPF myths you need to know

It's summer and boat trip season! If you live in Hong Kong, how can you get away without some gorgeous #summertan? The reason I was inspired to write this post is because I recently came across an "organic beauty" brand that promotes the use of their coconut oil as sunscreen. My response is...

What the fuck?


The basics



UV radiation can be classified as UVA, UVB, or UVC.

UVA (a cue to remember is A for Aging):

  • Longest wavelength among the three,

  • up to 95% of UV radiation reaching the Earth’s surface.

  • 30 to 50 times more prevalent than UVB.

  • It penetrates the skin more deeply than UVB, has long been known to play a major part in skin aging and wrinkling (photoaging), and suspect to cause skin cancer under prolonged exposure.

  • Similar intensity during all daylight hours, can penetrate clouds and glass.


  • Shorter wavelength than UVA, but chief cause of skin reddening and sunburn. UVB rays do not significantly penetrate glass.

Most UVC is absorbed by the ozone layer and does not reach the earth, so we don't have to worry about it for now.

You see, the main enemy is UVB and more importantly UVA because of its ubiquity and “invisible” impact (you don’t know you’re ‘burnt’ because you’re skin won’t turn red).

spf only does part of the job

Anyone who tells you that you only need SPF is only telling you half the story.

SPF refers to 'sun protection factor': how long you can stay in the sun without getting sunburnt while wearing that product. Say if you normally get a sunburnt in the sun after 30 minutes, then applying an SPF of 15 means you can stay under the sun without getting sunburnt for 15 times of your normal 'sunburnt threshold', so 30 mins x 15 = 7.5 hours. It is not a fixed degree of protection. What I'm trying to say is, an SPF of 15 on you is not of equivalent strength on your bestie.

Having a high SPF sunscreen isn't the end of the story. SPF only protects against UVB.

For UVA, you need PA (Protection Grade of UVA grading). 


the common misconceptions

(1) Applying SPF 15 doesn't mean you get SPF 15 protection

Nope. It depends on how much you put. Applying too little of the sunscreen gets you less SPF, and applying too much, no matter how much more, will only get you  SPF 15 - it doesn't add up and go above 15.  According to the Skin Cancer Foundation [1], "to achieve the SPF reflected on a bottle of sunscreen, you should use approximately two milligrams of sunscreen per square centimeter of skin. In practice, this means applying the equivalent of a shot glass (two tablespoons) of sunscreen to the exposed areas of the face and body – a nickel-sized dollop to the face alone." In reality, most of us don't wear that much, so if SPF 15 is the recommended protection level, most of us are not wearing enough. Perhaps a way is to buy higher SPF, and apply the same amount as we would for SPF 15, so as to increase our protection level?


(2) No sunscreen is 'perfect'

No sunscreen can block all UV rays. SPF 15 filters out approximately 93% of all incoming UVB rays. SPF 30 keeps out 97% and SPF 50 keeps out 98%. And we're just talking about UVB. In Asia, a lot of our sunscreen includes PA grades, which is great. In Western countries, you might see some sunscreen with the word 'broad spectrum', referring to UVA protection.


(3) SPF 80 is NOT much better than SPF 50

Depends what your 'much' means, but SPF above 50 doesn't get much more protection than SPF 50. In fact, the US FDA had a proposed rule in 2011 that they would ban products labelling itself as SPF 50+ because "there is not sufficient data to show that products with SPF values higher than 50 provide greater protection for users than products with SPF values of 50" [2]. This might mislead consumers to think that they have enough protection under the sun without reapplying. 


(4) Water-resistant does not mean it is water-proof

Water-resistant does not mean water-proof. It will still wear off at some point. Make sure you re-apply sunscreen every 1 hour or so, even though it says water-resistant. In US, to be a 'water-resistant' sunscreen, it means the label’s SPF’s value has been measured after application, 40 mins of water immersion, and/or 80 minutes of water immersion [2].  If, a sunscreen has a measurement of SPF 60 after application before submersion, but drops to SPF 55 after 40 mins of water immersion, the manufacturer can choose to list either "water-resistant 40 mins, SPF 55" or "SPF 60 (but no water-resistant)". In the US, water-immersion tests must go through cycles of 20 mins of immersion of water + 15 mins of drying, repeat to accumulate 40 & 80 mins of water immersion [3].

But the SPF claim only remains true if you’re not brushing off or touching your skin throughout. Notice that even if the water-resistant test is quite vigorous and designed to simulate real swimming scenarios, what it didn't include is the swimmer touching the skin, wiping sweat, or towelling his/her body dry.

To know more about ingredients used in water-resistant sunscreens and their pros & cons, see here


(5) Apply sunscreen as the last item, after your foundation

If you apply sunscreen and then your moisturizer or foundation, you are diluting / breaking the sunscreen you've applied.  Moisturizers and some foundations contain high level of water, and just as why you need to reapply sunscreen after you go into water, you would need to do the same!

If you're wearing creamy foundations, if you're sure you're not smoothing it and not wiping off the sunscreen underneath, that should be better. But I understand how your foundation would look smudged if you apply sunscreen over it, hence, the recommendation would be to wear sunscreen + foundation with SPF, trying to balance it off...


So... is coconut oil a sunscreen?

Well... Anything can be a sunscreen, you can put a layer of fruit juice on your skin and it will still have some level of SPF. Your question should be, whether coconut oil is an effective sunscreen.

There are studies which tested various oils and conclude that their SPF value is close to 1 (means nothing), while other studies find that oils will have the SPF value ranging 1 – 8. For more, see this link. Mind you, the Skin Cancer Foundation considers SPFs of 15 as the minimal protection for normal everyday activity. Plus there are studies looking into the impact of oil on skin as they are heated up.

The most important point is, coconut oil does not protect you from skin-aging UVA. This means, when you use coconut oil as tanning oil, you get what you want – you get tanned, and you’re also aging your skin. Oils can be a good emollient that creates a smooth and longer-lasting film on skin, so at best oils can complement the sunscreen to make it more evenly distributed, but it, on its own, is not a good sunscreen.


What sunscreen should I wear?

There are two types of sunscreen: Physical and Chemical.

Physical sunscreen means it is deflecting rays, and chemical sunscreen means it is absorbing rays. It is not that the chemical sunscreen cannot protect you from rays, it is just that some claim that they can be hormone disruptors or cause skin irritation. Physical / mineral sunscreens tend to rate better according to EWG, as they are usually chemicals with lower toxicity [4]. I didn't read into that so I can't say for sure, but I did have the following table from the FDA with a list of approved sunscreen chemicals:

As you can see, Zinc oxide and titanium dioxide are really the clear winners in covering UVA & B!

Titanium dioxide is commonly found in make-up products because of its white colour. That is why sometimes physical sunscreen can be very white on the face!  

Also you might find these 2 ingredients in non-sunscreen products. It is important that you know even if this ingredient is found, it doesn't mean it is automatically a sunscreen, because the concentration matters, and that for a product to claim their sunscreen properties, it has to undergo testing. Say, titanium dioxide is an "active ingredient", meaning they will always show at the first of the ingredient list on US products, regardless of their concentrations. But in the UK, they are listed according to concentrations [5].


My Final Recommendation

1) Coconut oil is good - put it as the base layer BEFORE you put your sunscreen. It helps to smoothen out skin for your sunscreen.

2) Stick to zinc oxide & titanium dioxide, but do NOT inhale when you put it on if it is in powder form [6].

3) Also avoid ones that claim 'nanoparticles', because research today has not done enough to confirm whether nanotechnology is safe or not [7].

4) Depending on your goal to tan or not tan, you can choose SPF ranges but YOU MUST SELECT PA +++ products!!


last but not least,