The Science of Sunscreen with Katherine Engel


Guest Post by Katherine Engel from Chrysalis Medispa

In my role as a skincare therapist at a medispa, which is attached to a plastic surgeon’s office, I talk my head off every day about the importance of protecting the skin from UV exposure.  My clients range in variety from young teenagers to busy mums and dads, along with older men and women who are undergoing facelifts and laser resurfacing.  One common thread that runs between all these clients is a basic lack of understanding of how to best protect their skin from the sun, and why it is necessary to do so.

Broadly speaking, there are two main types of sun protection you can use in a topical lotion on your skin – chemical (“sunscreen”) and physical (“sunblock”).  The difference between these lies in their active ingredients.  Chemical sunscreens rely on ingredients that sink into your skin and provide a “filter” which absorbs and screens UV rays.  Physical sunblocks sit on top of the skin and contain mineral ingredients that provide a physical block which prevents UVA & UVB rays from penetrating into the skin and causing cell damage.  While neither is necessarily “better” than the other, I like to use the analogy that chemical sunscreen is like your home’s screen door whereas physical sunblock is like your wooden front door.  By this reasoning you’d think that it’s a no-brainer to always use a physical sunblock, but that’s not always the case.  Choosing the right sun protection for your skin is a very individual choice.


Recommended by Katherine: Invisible Zinc Face & Body Sunscreen SPF 30+ UVA-UVB (physical); Olay Complete Defence for Sensitive Skin SPF30 (chemical); Shiseido Gentle Sun Protection Lotion for Sensitive Skin and Babies (physical); Aspect Envirostat Handsfree 30+ (chemical) – not shown; Cosmedix Reflect SPF15 (physical) – not shown

Often, chemical sunscreens are much more pleasant to wear as they tend to be lighter and more comfortable formulations – so our compliance in wearing them tends to be a little better.  They are also, by and large, more waterproof than physical sunblocks because they actually sink in to the skin and provide a nice little shield over the cells themselves (this is the reason they absolutely must be applied to clean, bare, dry skin).  So you can sweat and swim and your sun protection will remain consistent (according to its labelling  – look for “4 hours water resistant” or similar).

However, physical sunblocks do have their merits too.  All things being equal, they do provide a better protection.  They are also a far better choice for those who are allergic to chemical sunscreens or have trouble tolerating chemical ingredients like PABA.  And – importantly for me – they don’t need contact with completely bare skin, so they can be applied over your morning serums and moisturisers.

I personally like a physical sunblock for everyday wear, but if I know I’m going to be exposed to the sun, I will often layer a physical sunblock over a chemical sunscreen for the ultimate protection.  However, it’s really up to the individual.  Often a chemical sunscreen is the perfect choice for kids, teens, and men because of the barely-there texture which can be achieved in the latest formulations.  Say goodbye to that sticky “beach sunscreen” feeling!  Sunscreens and sunblocks are so well-made now, there is really no excuse for not wearing daily sun protection.


Whatever sun protection you do end up choosing, it’s important that it be used properly. This means reading the label and applying the product as instructed.  Like I said above, chemical sunscreens need contact with bare skin, so if you’re applying a chemical sunscreen over your morning skincare products, you’re doing yourself a huge disservice and missing out on all that wonderful protection.  A decent amount needs to be applied too. There’s no use applying the size of a pea when the recommended amount is half a teaspoon, which is more like four or five peas!  There are many beautiful sunscreens on the market now which aren’t expensive, so there’s really no reason to scrimp.

Stay tuned for part two where I will explain, among other things, why reapplication of sunscreen is important but why it’s also something that so many people (including so many parents!) get terribly, dreadfully wrong.

Katherine has been passionate about skin her entire life, and in her mid-twenties decided to turn this passion into a career.  She has previously worked in boutique salons and spas for five years, providing luxury beauty and skin treatments and advice to men and women from all walks of life.  Currently Katherine is a fulltime skin therapist in a large high-end medispa, which provides high-performance peels, advanced skincare, laser, Coolsculpting, and injectables. She works extensively with clients to refine their home skincare routines, as she is passionate about optimising results for her clients.  She believes in utilising the best ingredients, with the best delivery systems, to maintain healthy skin and to prevent damage as much as possible before it begins. Katherine has a special interest in ingredients and cosmetic chemistry formulations.  She is also currently studying a Bachelor of Nursing Sciences full-time.

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