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Dr Davin Lim's Guide To Sunscreen Application

Updated: Oct 13

By Dr Davin Lim


Best Used: Twice a day

Caution: Use correctly

Best for: Everyone & everything

Comments: The absolute foundation of skin care

Mode of action: Protects against UV radiation

Science Score: ☆ ☆ ☆ ☆ ☆





What is the skin science behind sunscreen?


The absolute cornerstone of any skin care routine revolves around sunscreens. Did you know UV rays account for over 90% of skin ageing, also known as photoaging? Yep, this is especially true in the sunshine state - Queensland, Australia. Not only does UV exposure cause cosmetic issues including melasma, pigmentation & wrinkles, it can also cause skin cancer. Yes, it is true that 2 out of every 3 Australians will develop either sunspots or skin cancer by the age of 55... pretty scary stats!

Finding the best sunscreens for you can be perplexing as there are so many brands & formulations, I hope this page will give you a guide. Here's everything you need to know to find the best SPF, as recommended by Davin Lim.

*What do I know about sunscreens? I spent my registrar training in the subspecialty of photobiology & photodermatology in the UK, Scotland & Ireland. I have authored a few papers on sunscreens & have been fortunate enough to have had clinical training by world renowned bosses in these countries. Blessed!


What’s the difference between mineral & chemical sunscreens?


Mineral and chemical sunscreens are both effective at protecting you from ultraviolet radiation, however they work in different ways. Chemical sunscreens with ingredients absorb and change UV radiation into heat, which doesn’t cause much damage to the deep layers of skin. Recent science suggests that mineral sunscreens may do this too, in addition to reflecting UV & visible rays

Mineral sunscreens or physical blockers contain zinc oxides, titanium dioxide as well as iron oxides (Iron oxide sunscreens are not available in Australia, however can be sourced overseas). For many decades mineral sunscreens were thought to reflect UV radiation, however studies in the past 5 years have shown they act much like chemical sunscreens, with reflection accounting for only 5% of their activity in the UV spectrum, but accounting for the majority of attenuation in the visible spectrum.

Most new formulations are hybrid sunscreens, combining both physical & chemical blockers. The majority of dermatologists will advise hybrids but patients with super sensitive skin, for example rosacea, dermatitis, eczema often prefer 100% physical blockers such as Invisible Zinc. This is due to the fact chemical sunscreens are more likely to cause irritation, however allergic & photoallergic reactions are extremely rare. If you fall in the later category, your medical dermatologist may undertake patch & photopatch testing.

As reinforced throughout this website & my numerous social media posts, don’t fuss over the brands, get into the habit of using sunscreens properly before worrying about the finer details.


So what is the best sunscreen for me?

The best sunscreen is the one that you are going to apply every single day, in fact twice a day. My top 3 formulations are Melan 130 (very expensive but nice), La Roche Posay Anthelios (light, affordable) & Invisible Zinc (cost effective, high protection). Obviously the feel of a sunscreen is a subjective opinion!

Remember this checklist when choosing the right formulation for your skin type:

  1. You need it every single day. You’re still exposed to UV rays when it’s cloudy & most importantly forming a habit so that you are not caught out when the weather changes. So it’s important not just to find a sunblock you’ll wear on trips to the beach, but also to find the best daily face sunscreen for your skin.

  2. You need TWO types of sunscreen. One as a daily (as above) and the other if you are into outdoor activities including contact with water. This ‘active’ sunscreen should be waterproof & last 2, preferably 4 hours. Ego Sport or Neutrogena make really gooey sticky, stuff that sticks. They are also cheap, so lather it on.

  3. Reapply! Just putting sunscreen on once in the morning isn’t always enough, especially if you’re going to be out in the sun for a few hours. You should be reapplying at midday, or just before your daily commute home. If you apply in the morning under your makeup, and then you’re inside at work all day, you’re probably good (keeping in mind that you’ll have to reapply at some point)

  4. Price point - go for feel, not cost. Just because something is expensive doesn’t mean it’s better. In fact for sunscreens, the more expensive the product, the less application amount and frequency. So pick a sunscreen that suits your budget.

  5. Skin of color still needs sunscreen. Even if you do not burn, sunscreen is super important to project your dermis and collagen. More importantly a high factor SPF can prevent pigmentation changes such as melasma & post-inflammatory hyperpigmentation.

Ultimately, there are a ton of sunscreens out there and they can feel different to different people. So don’t be discouraged if you don’t like one—just keep trying. A try before you buy policy is not just Asian mentality, but it should be applied to your sunscreen purchases.


What is the correct amount of sunscreen to use?

Fact - 95% of people underdose their sunscreen. Did you know the SPF measurement is not only determined by the constituents in sunscreen, but most importantly by the amount of sunscreen? SPF is partly determined by application of 2mg per cm2 of product. This equates to between 3.5 to 4.5 ml needed to cover the head & neck. Half this dose & you are effectively halving the SPF. So, before you start worrying about ingredients, UVA vs UVB protection, photo allergies & all the minuscule details, start by the correct application amount, then frequency. My ‘2’ rule for sunscreen is ‘two fingers of sunscreen, twice a day, two types.’

Is applying sunscreen once a day enough?

The truth is, it depends. If you do not have any skin care goals & you work indoors, yes, probably fine to apply once a day. This goes against the grain of my fellow dermatologists who preach application every 4 hours (some even 2 hours). Let’s do some quick math, correct application amount average 3.5 mls face, neck & decolletage. If you do 3 times a day application, that means 10 mls per day. One average bottle of sunscreen is 50 ml. Hence you will go through 6 bottles a month. I don’t think any sane dermatologist uses this much sunscreen. Same analogy goes for dentists, brush after every meal, 5 meals per day, would most dentists brush this often?

Now if you are trying to correct a skin problem or concern, well, that is a different matter. If you have melasma or a similar pigmentation problem, then yes, you do need to apply sunscreen at least twice a day. That is not negotiable.

What goes on first, sunscreen or moisturiser?

If you are using sunscreen in either a lotion or cream (most formulations), you want to put that on after your moisturiser. This is because if you mix it in with your moisturiser, you're diluting your sunscreen and its ability to protect. The quickest way to working out how much SPF protection you're actually getting goes like this... If you use half the correct amount of sunscreen, you effectively half the SPF. So, if your sunscreen is 30+, and you dilute roughly 50% of it in moisturiser (or use half the recommended amount), your SPF is now 15. So, do not dilute your sunscreen!

What's the difference between SPF 30 and 50, is higher better?

An SPF 30 allows about 3% of UVB rays to hit your skin. An SPF of 50 allows about 2% of those rays through. That may seem like a small difference until you realize that the SPF 30 is allowing 50% more UV radiation onto your skin. So, yes, higher the SPF the better, refer to below for the explanation.

What does the SPF rating of sunscreen mean?

The SPF number tells you how long the sun’s UVB radiation would take to redden your skin, known as the MED or minimal erythema dose. So ideally, with SPF 50 it would take you 50 x longer to burn than if you weren’t wearing sunscreen.

The fact that SPF is tested under ideal laboratory conditions using a specified amount of sunscreen (thick application) makes this difference even more marked. Half the amount of sunscreen, effectively halves the SPF. Hence, that is why it is better to get a higher SPF to compensate for application amount. Choosing at least a 30 + SPF is good however, 50 is better.

What is best - lotion, cream or spray?

Lotions & creams are best. The former gives a lighter feel. Dermatologists do not recommend sunscreen sprays simply because it is extremely challenging to deliver an application that is thick enough to give the advertised SPF. One of the only exceptions would be back application. We acknowledge that it is difficult to self apply sunscreen to your back and a spray formulation in this situation is sensible.


Do I need to wear sunscreen if I am indoors?


Excellent question, very complex answer. In the context of ‘radiation’ from computer screens & devices, the absolute answer is *no. In the context of UV from sitting next to a window, the answer is ‘it depends’. Window glass doesn't protect against UVB, hence you will get burnt. UVA is partially attenuated by some types of glass, &, fully attenuated in the minority. Unless you absolutely know what type of glass you are sitting to, you should ideally wear sunscreen if you are sitting next to a closed window. This is especially important if you have melasma pigmentation.

*Unless you have a photosensitive dermatoses such as porphyria or idiopathic photodermatoses (CAD, H. vacciniforme, actinic prurigo) or other rare conditions, light from electrical devices will have no impact on conditions such as melasma, pigment etc.

Why is sunscreen so vitally important in the management of melasma?

Fact: If you do nothing but adhere to the proper use of sunscreen, your melasma will improve by up to 50%. Sobering fact but true. Research has shown that the MASI or Melasma Area Severity Index improves by 50%. What is proper use? 3 to 5 mls of sunscreen at least TWICE a day. The best sunscreens are either hybrid sunscreens or physical sunscreens that contain zinc or titanium dioxide. Start with adequate photoprotection, then explore other treatments including pigment correctors, lasers & chemical peels.

Note: Sunscreens only protects UVB & UVA, hence you will still have visible & infrared light. This is the main reason why melasma still requires other treatments to reduce the activity of the pigment cell.

What about sunscreens & rosacea?

The biggest flare factor for rosacea is sunlight exposure, reported to flare up this condition in over 80% of sufferers. In Brisbane, Australia, I see 2 peaks of flare ups, one around June with the cooler temperatures meaning more indoor heating, & the other in August & September with westerly winds & an increase in UV heading towards spring. Rosacea patients fall in the category of sensitive skin and finding a non-irritating sunscreen can be complex. Here are some hints:

  1. Physical blockers are less irritating. Consider Invisible Zinc.

  2. Hybrid sunscreens like La Roche Posay are usually well tolerated

  3. Try before you buy

  4. Use hat & umbrellas (especially if you goto the beach)

Why are sunscreens important in the management of acne scars?

3 words - Post Inflammatory Hyperpigmentation or PIH. This type of acne scar is known as type 1 - 2 acne scars, changes pigment. Here are some of the facts - 50% of acne patients will have this type of scarring for longer than one year. 25% will persist for 5 years or more. Sunscreens can markedly decrease the chances of PIH or colour changes. Finding a light sunscreen that doesn’t clog your pores can be challenging but my favourite choices are La Roche Posay or Invisible Zinc. If you do suffer from PIH or post acne marks, my nurses @cliniccutis can provide simple cost effective solutions.

Which areas are frequently missed during sunscreen application?

Now time for the finer pointers of how to correctly use sunscreens. Don’t forget these often-ignored body parts:

  1. Neck & decolletage areas, ranks as the number two spot to apply sunscreen. The recommended dose of 3 to 5 mls includes your neck, however do not forget your chest & decolletage areas. Photoaging is commonly seen in these sites.

  2. Hairline & top of your head, especially important if one has thin hair - low hair density. Grabbing a hat is a great alternative, but that sunscreen is necessary if you plan to remove the hat, additionally Also don’t neglect your hairline- both front sides, & back.

  3. Ears, applying sunscreen behind your ears, onto their tops, sides, & bottom. Generally speaking, missing your ears once & getting sunburn will put you on the road to forming a habit in the future. Sunburn ears means many nights of uncomfortable sleep. Skin cancers including basal cell tumors & squamous cell cancer are trophic to the ears; so don’t forget your sunscreen.

  4. Eyelids are also trophic for skin cancers. Consider a mineral sunscreen if you have super sensitive skin. Less fashionable sunglasses can give excellent protection.

  5. Hands, the tops of your hands are always exposed to ultraviolet & visible light when you’re outside. Akin to your lips you may need to be extra aware of reapplying sunscreen to this spot.

How long is sunscreen effective after applying?


A sunscreen sun protection factor (SPF) is only fully effective for 2 hours after you put it on. It depends on many factors including the formulation (waterproof or not), as well as your activity. I do not agree with some of my colleagues who insist on applying sunscreen every 2 hours (in the context of daily habis, not management of photodermatoses). Get real, if you are living in the Northern Hemisphere or even in Australia when the sun shines 12 hours or more a day, are you really going to re-apply 6 times a day, at 3.5 ml each application? Probably not. That’s close to 20 mls daily, hence an average bottle lasts less than 3 days? Great to give this figure, but is it really practical? You make that decision!


What is a natural sunscreen for face?


Natural sunscreens are the "physical sunscreens" I talked about earlier, containing zinc oxide & titanium dioxide. Note that all sunscreens contain chemicals, including ingredients not listed on the bottle/tube. Now, if you really want to go all natural without any nanoparticles, the most ‘natural formulation’ is clay. Thick coat on & it offers an SPF of greater than 1000. The pros & cons of this are obvious.

Can vitamin D levels be too low with sunscreen?

The best source of vitamin D is UVB radiation from the sun. UV radiation levels vary depending on location, time of year, time of day, & cloud cover. For most people, adequate vitamin D levels are reached through regular incidental exposure to the sun, however if you are great with sun protection, your levels may be low. If so, pop a vitamin D tablet. Simple as that. We take supplements including fish oil, vitamin E, hair, nail, skin formulations, collagen supplements that don’t work, folic acid, vitamin C & echinacea & a whole lot more. What’s the big deal with vitamin D supplements? I really can not see the other side of the argument, and yes, I am biased because I am a dermatologist.

Davin’s view on Sunscreens

I think everyone is trying to make things so much more complex than it needs to be. Here is my take- buy something you are going to actually like using. Buy it, use it daily. If you have a skin condition that you want to improve, for example, melasma, pigmentation, fine lines, you do need to use it at least twice a day. You do need a sticky gluey sunscreen if you run outside or you are in the water. You can not expect your daily to stick. Buy a sport formulation & use it alot, not sparingly. Once you get this down pat, then sure you can look at the finer things such as UVA vs UVB protection, chemicals, photostability, photoallergic potential etc.. and geek out. Until then, start with the basics. End of discussion.


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