Chemical vs Physical Sunscreens: The Science (with video)

Video: Chemical vs Physical Sunscreens: The Science

Video: Chemical vs Physical Sunscreens: The Science

Are chemical or physical sunscreens better? I touched on this in my Sunscreen and Make-up video, but a lot of people have been asking me to talk more about it, so I’ve expanded on the topic in this post, which comes in video form as well!

Click here for the video – scroll down for the blog post “summary” version with references and product recommendations (which is still somehow 1500+ words long…).

What Are Chemical and Physical Sunscreens?

The active ingredients in sunscreens are often divided into two categories:

  • Physical sunscreen ingredients (more correctly known as inorganic sunscreen ingredients) are zinc oxide and titanium dioxide.
  • Chemical sunscreen ingredients (more correctly known as organic sunscreen ingredients) are everything else.

You can have sunscreens containing only organic filters, only inorganic filters, or a combination of both.

Video: Chemical vs Physical Sunscreens: The Science

The reason organic (carbon-based) and inorganic (not carbon-based) is a better classification than chemical/physical is that there’s overlap between how they work. Both types work by absorbing UV and turning it into heat. Inorganic sunscreens also scatter and reflect about 5-10% of the incoming UV, as do some particulate organic sunscreens like Tinosorb M, so really they should be classified as both chemical and physical.

Differences Between Chemical and Physical Sunscreens

The big differences between them that you should consider are:

Protection Level

SPF 50+ is pretty common with both types of sunscreen, but broad spectrum protection (that includes protection against longer wavelengths of UVA) is where there’s a difference.

Organic sunscreens give higher, photostable protection from UVA if you use newer filters like Tinosorbs S and M, and Uvinul A Plus (not yet available in the US). The more common avobenzone gives really high UVA protection, but it breaks down in UV so you have to be diligent about reapplication (although some formulas stabilise avobenzone so it breaks down slower, and you should diligently reapply sunscreen anyway if you’re spending a lot of time in the sun).

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Video: How Much Sunscreen Do You Need For Your Face?

Video: How Much Sunscreen Do You Need For Your Face?

Video: How Much Sunscreen Do You Need For Your Face?

You’ve probably heard that you need 1/4 teaspoon of sunscreen to cover your face. This quantity is calculated from an estimate of people’s face sizes, and the amount of sunscreen they use in SPF testing (2 mg per cm2). Since it’s based on the thickness of sunscreen, a larger face will need more sunscreen, while a smaller face will need less sunscreen. But how much sunscreen would I need?

Because I have an unusually large forehead and a flat-but-wide nose, I didn’t want to use a rough geometric estimate, and opted for a more empirical (and hopefully accurate), fiddlier measurement method instead. I decided to work out my facial surface area by covering my face with paper tape, then taping it onto grid paper and counting the area. Of course, I filmed the process! I then worked out how much sunscreen I needed for my face, and I also worked out how much sunscreen I needed for my neck and decolletage.

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Video: Do Collagen Supplements Work for Wrinkles and Younger Skin?

Video: Do Collagen Supplements Work for Wrinkles and Younger Skin?

Supplements are one of the big new “it” categories in beauty, and collagen supplements are one of the most popular. Oral collagen supplements are supposed to be anti-aging, get rid of wrinkles and plump up skin so it looks younger. What’s the science behind them and do they really work?

I made a video on the topic! In it I talk about the way collagen supplements could theoretically work, and then break down the clinical studies on eating and drinking collagen.

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Mythbusting: Are Vitamin C Serums Bad for You?

Mythbusting: Are Vitamin C Serums Bad for You?

I’ve been asked a lot for my opinion on a recent article on whether vitamin C serums are bad for your skin. In the article, Wendy explains why Oumere will never have a vitamin C serum in their line. She outlines that vitamin C can:

  • Act as a pro-oxidant when it reacts with iron in the air (or iron and copper in cosmetics) via the Fenton reaction, leading to irritation, collagen and elastin breakdown and acne
  • Lead to desensitisation (tachyphylaxis) so if you start using it too young, your skin won’t respond later on

Let’s take a look at both of these arguments.

Is Vitamin C Pro-oxidant?

While in some circumstances vitamin C can act as a pro-oxidant after it reacts with metals and potentially lead to collagen destruction, vitamin C is also known to have effects that are the exact opposite:

  • Vitamin C on its own is a potent antioxidant that soaks up free radicals and prevents the oxidative damage that results from UV light and other environmental stressors, as well as normal biological processes
  • Vitamin C is an essential cofactor that’s required for enzymes that crosslink and stabilise collagen (prolyl and lysyl hydroxylase)

Mythbusting: Are Vitamin C Serums Bad for You?

So how do we tell which of these actions, pro-oxidant or antioxidant, wins out? Science, of course! More specifically, we have quite a lot of clinical trials on vitamin C where vitamin C serums are applied to actual human skin, and its effect is measured. Vitamin C is one of THE best researched skincare ingredients.

None of the clinical trials on topical vitamin C (that’s vitamin C applied to the skin) found a decrease in collagen. In fact, a whole bunch of studies found that vitamin C increased collagen. In these studies, the volunteers were also exposed to air pollution and other cosmetic products, which were proposed to be the sources of metals that would cause a pro-oxidant effect in the article. Clearly the antioxidant effect is winning.

Related Post: Antioxidants in Skincare: What Do They Do?

Studies where vitamin C increased collagen:

Most studies on vitamin C measure its effect on photodamage. These studies generally measure the effect of vitamin C on wrinkles. While this isn’t a direct measure of collagen, lack of collagen causes deeper wrinkles, so if vitamin C was having a pro-oxidant effect you’d see a worsening of photodamage (which is actually caused partially by increased oxidation). In these studies, vitamin C improved photodamage:

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Why Vitamin C Can Stain Your Skin (and How to Avoid It!)

Why Vitamin C Can Stain Your Skin (and How to Avoid It!)

Vitamin C is one of the few skincare ingredients with a ton of independent research to back up its properties, like its brightening and anti-wrinkle benefits. Those of you who are vitamin C enthusiasts may have noticed that with some vitamin C serums, you end up with slightly stained orange-brown skin after a few days of use – sort of like fake tan. I’ve often wondered why but didn’t really dig into it past a quick Google search (which found nothing), so I just put it off as a weird side effect of vitamin C oxidising.

But recently, I came across a diagram in a peer-reviewed paper on a completely different topic that accidentally told me exactly why vitamin C does this: ascorbic acid eventually oxidises to erythrulose!

Why Vitamin C Can Stain Your Skin (and How to Avoid It!)

As most of you may know, vitamin C in the form of ascorbic acid oxidises easily to dehydroascorbic acid, which has an orange-brown colour. It does this when it’s stored in water, as well as on your skin. Oxygen and light exposure will speed up the oxidation reaction. This reaction is reversible, so you can get back the ascorbic acid if you have the right antioxidants in the formula.

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Do I Need a Special Cleanser to Remove Sunscreen?

Do I Need a Special Cleanser to Remove Sunscreen?

Here’s a myth I’ve been seeing around skincare communities: that you have to use a special cleanser to remove water-resistant sunscreen. For example:

“Keep in mind that most of these sunscreen actives are also oil-soluble (only dissolves in oil, not water), which gives sunscreens their water-proof and sweat-proof properties. Therefore, in order to completely remove sunscreen, you have to use an oil, cleansing oil, emollient cleanser, or makeup remover of some kind.” (Source: Skinacea)

Have we all been leaving sunscreen on our faces before we discovered the magic of double cleansing??

Do I Need a Special Cleanser to Remove Sunscreen?

How Do Cleansers Work?

Luckily, the answer is no. A regular cleanser will remove waterproof sunscreen! The reason for this is surfactants.

Surfactants are a special class of chemical I’ve mentioned quite a few times before. They look a bit like a tadpole, with a lipophilic (oil-loving) “tail” and a hydrophilic water-loving) “head”.

Do I Need a Special Cleanser to Remove Sunscreen?

(Related posts: How Do Cleansing Balms Work?, How Does Micellar Water Work?, The Science of Face Washing)

Because of this special structure, surfactants can help oil dissolve in water and vice versa. The tail binds to oil while the head binds to water. The surfactants help the oil lift off the skin, forming little oil droplets that end up dispersed in the water as an emulsion (surfactants are also known as emulsifiers for this reason). The droplets can then be rinsed away, leaving your skin clean.

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The Pros and Cons of Accutane (Isotretinoin) for Acne

The Pros and Cons of Accutane (Isotretinoin) for Acne

This is a guest post from Facing Acne.

In the history of acne treatments, there has never been a medication that has caused more controversy than Accutane. There is also no treatment that has ever produced such startling results. For this reason, Accutane has both its passionate defenders and its equally passionate detractors. The choice of whether to try Accutane is a very difficult one. All the factors must be properly weighed, and if you are considering this option, you should be fully aware of all of the possible side effects as well as the nearly miraculous efficacy of this drug in clearing even the most severe cases of acne.

The Pros and Cons of Accutane (Isotretinoin) for Acne

A hyperaggressive treatment like Accutane should only be considered when other, more conventional treatments have been exhausted with unsatisfactory results. With so many options on the market, it is likely that one of them will fit your skin type and help give you relief from acne. (Related: Does Proactiv really work?) Many people have questions about the more common treatments and it can be overwhelming trying to sort through all of the options. But if you are a long-time acne sufferer, it is worth the effort. Here we take a closer look at Accutane and answer at least some of the most common questions in relation to this well-known, highly debated, and very controversial acne treatment solution.

How Does Accutane Work?

First of all, what is Accutane? Accutane is the brand name of the drug isotretinoin, which is a derivative of vitamin A. It is administered in pill form, usually for somewhere between 15 and 20 weeks. It works primarily by reducing the amount of sebum your skin produces and by helping your skin regenerate faster, thus healing existing lesions and evening out skin tone by eliminating any residual redness.

Different dosages are used depending on the severity of the condition. Higher dosages have a greater rate of effectiveness and a lower relapse rate, but also come with a heightened risk of side effects.

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Fact-check Feature: How to choose a moisturiser

NoTS 28 Remedy Perfect Solution Set Skincare Review

Choosing your moisturiser can be a difficult process. The beauty section is full of moisturisers for different skin types, but I’m sure many of you have had the annoying experience of taking a moisturiser home that’s supposed to be for your skin type, then finding that it’s just wrong. What can you do? The most foolproof way to improve your …

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