What’s the difference between physical and chemical sunscreens? And which one should you choose?

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Sun exposure can accelerate ageing, cause skin burns, erythema (a skin reaction), skin cancer, melasmas (or sun spots) and other forms of hyperpigmentation – all triggered by solar ultraviolet radiation.

Approximately 80% of skin cancer cases in people engaged in outdoor activities are preventable by decreasing sun exposure. This can be done in lots of ways including wearing protective clothing or sunscreens.

But not all sunscreens work in the same way. You might have heard of “physical” and “chemical” sunscreens. What’s the difference and which one is right for you?

How sunscreens are classified

Sunscreens are grouped by their use of active inorganic and organic ultraviolet (UV) filters. Chemical sunscreens use organic filters such as cinnamates (chemically related to cinnamon oil) and benzophenones. Physical sunscreens (sometimes called mineral sunscreens) use inorganic filters such as titanium and zinc oxide.

These filters prevent the effects of UV radiation on the skin.

Organic UV filters are known as chemical filters because the molecules in them change to stop UV radiation reaching the skin. Inorganic UV filters are known as physical filters, because they work through physical means, such as blocking, scattering and reflection of UV radiation to prevent skin damage.

Nano versus micro

The effectiveness of the filters in physical sunscreen depends on factors including the size of the particle, how it’s mixed into the cream or lotion, the amount used and the refraction index (the speed light travels through a substance) of each filter.

When the particle size in physical sunscreens is large, it causes the light to be scattered and reflected more. That means physical sunscreens can be more obvious on the skin, which can reduce their cosmetic appeal.

Nanoparticulate forms of physical sunscreens (with tiny particles smaller than 100 nanometers) can improve the cosmetic appearance of creams on the skin and UV protection, because the particles in this size range absorb more radiation than they reflect. These are sometimes labelled as “invisible” zinc or mineral formulations and are considered safe.

So how do chemical sunscreens work?

Chemical UV filters work by absorbing high-energy UV rays. This leads to the filter molecules interacting with sunlight and changing chemically.

When molecules return to their ground (or lower energy) state, they release energy as heat, distributed all over the skin. This may lead to uncomfortable reactions for people with skin sensitivity.

Generally, UV filters are meant to stay on the epidermis (the first skin layer) surface to protect it from UV radiation. When they enter into the dermis (the connective tissue layer) and bloodstream, this can lead to skin sensitivity and increase the risk of toxicity. The safety profile of chemical UV filters may depend on whether their small molecular size allows them to penetrate the skin.

Chemical sunscreens, compared to physical ones, cause more adverse reactions in the skin because of chemical changes in their molecules. In addition, some chemical filters, such as dibenzoylmethane tend to break down after UV exposure. These degraded products can no longer protect the skin against UV and, if they penetrate the skin, can cause cell damage.

Due to their stability – that is, how well they retain product integrity and effectiveness when exposed to sunlight – physical sunscreens may be more suitable for children and people with skin allergies.

Although sunscreen filter ingredients can rarely cause true allergic dermatitis, patients with photodermatoses (where the skin reacts to light) and eczema have higher risk and should take care and seek advice.

What to look for

The best way to check if you’ll have a reaction to a physical or chemical sunscreen is to patch test it on a small area of skin.

And the best sunscreen to choose is one that provides broad-spectrum protection, is water and sweat-resistant, has a high sun protection factor (SPF), is easy to apply and has a low allergy risk.

Health authorities recommend sunscreen to prevent sun damage and cancer. Chemical sunscreens have the potential to penetrate the skin and may cause irritation for some people. Physical sunscreens are considered safe and effective and nanoparticulate formulations can increase their appeal and ease of use.The Conversation

Yousuf Mohammed, Dermatology researcher, The University of Queensland and Khanh Phan, Postdoctoral research associate, Frazer Institute, The University of Queensland

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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  • How does the drug abemaciclib treat breast cancer?

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    The anti-cancer drug abemaciclib (also known as Vernezio) has this month been added to the Australian Pharmaceutical Benefits Scheme (PBS) to treat certain types of breast cancer.

    This significantly reduces the cost of the drug. A patient can now expect to pay A$31.60 for a 28-day supply ($7.70 with a health care concession card). The price of abemaciclib without government subsidy is $4,250.

    So what is abemaciclib, and how did we get to this point?

    It stops cells dividing

    Researchers at the pharmaceutical company Eli Lilly developed abemaciclib and published the first study on the drug (then known as LY2835219) in 2014.

    Abemaciclib is a type of drug known as a “cyclin-dependent kinase inhibitor”. It’s taken as a pill twice a day.

    To maintain our health, many of the cells in our bodies need to grow and divide to produce new cells. Cancers develop when cells grow and divide out of control. Therefore, stopping cells from dividing into new cells is one way that cancer can be fought.

    When cells divide, they have to make a copy of their DNA to pass onto the new cell. “Cyclin-dependent kinases” (CDKs for short) are essential for this process. So, if you stop the CDKs, you stop the DNA copying, you stop cells dividing, and you fight the cancer.

    However, there are different types of CDKs, and not all cancers need them all to grow. Abemaciclib specifically targets CDK4 and CDK6. Thankfully, a lot of cancers do need these CDKs, including some breast cancers.

    Woman checks her breast
    The drug targets CDK4 and CDK6. Photoroyalty/Shutterstock

    But abemaciclib will only be effective against cancers that rely on CDK4 and CDK6 for continued growth. This specificity also means abemaciclib is fairly unique, so it can’t easily be replaced with a different drug.

    Two other CDK4/6 inhibitors were developed around the same time as abemaciclib, and are called ribociclib and palbociclib. Both of these drugs are also on the PBS for specific types of breast cancer. As the drugs differ in their chemical structures, they have slight differences in the way they are taken up and processed by the body. The preferred drug given to a breast cancer patient will depend on their unique circumstances.

    What are the side effects?

    Research is still ongoing into the differences between each of these CDK4/6 inhibitors, but it is known that the side effects are largely similar, but can differ in severity.

    The most common side effects of abemaciclib are fatigue, diarrhoea and neutropenia (reduced white blood cells). The gastrointestinal issues are generally more severe with abemaciclib.

    If these side effects are too severe, abemaciclib treatment can be stopped.

    What types of cancer has abemaciclib been approved for?

    In 2017, the United States Food and Drug Administration (FDA) approved abemaciclib for the treatment of patients with metastatic HR+/HER2- (hormone receptor-positive and human epidermal growth factor receptor 2-negative) breast cancer who did not respond to standard endocrine therapy.

    Australia’s Therapeutic Goods Administration (TGA) similarly approved abemaciclib in 2022 as an “adjuvant” therapy (after the initial surgery to remove the tumour) for patients with HR+/HER2- invasive early breast cancer which had spread to lymph nodes and was at high risk of returning.

    Doctor looks at laptop
    The drug is approved for people with early breast cancer which is at high risk of returning. PeopleImages.com – Yuri A/Shutterstock

    As of May 1 2024, the PBS covers this use of abemaciclib in combination with endocrine therapy such as fulvestrant, which is also listed on the PBS. Endocrine therapy, also known as hormonal therapy, blocks hormone receptor positive (HR+) cancers from receiving the hormones they need to survive.

    Could abemaciclib be used for other cancers in the future?

    Abemaciclib is of great interest to scientists and medical practitioners, and testing is ongoing to assess the effectiveness of abemaciclib in treating a range of other cancers, including gastrointestinal cancers and blood cancers.

    Abemaciclib may even be usable in brain cancers, as it has long been known to be capable of crossing the blood-brain barrier, a common stumbling block for potential anti-cancer drugs.

    Time will tell whether the role of abemaciclib in health care will be expanded. But for now, its inclusion on the PBS is sure to bring some relief to breast cancer patients nationwide.

    Sarah Diepstraten, Senior Research Officer, Blood Cells and Blood Cancer Division, Walter and Eliza Hall Institute and John (Eddie) La Marca, Senior Resarch Officer, Walter and Eliza Hall Institute

    This article is republished from The Conversation under a Creative Commons license. Read the original article.

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  • To Medicate or Not? That is the Question! – by Dr. Asha Bohannon

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    Medications are, of course, a necessity of life (literally!) for many, especially as we get older. Nevertheless, overmedication is also a big problem that can cause a lot of harm too, and guess what, it comes with the exact same “especially as we get older” tag too.

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    The book is prefaced and ended with pep talks that probably a person who has already bought the book does not need, but they don’t detract from the practical content either. Nevertheless, it feels a little odd that it takes until chapter 4 to reach “step 1” of her 7-step method!

    The style throughout is conversational and energetic, but not overly padded with hype; it’s just a very casual style. Nevertheless, she brings to bear her professional knowledge and understanding as a doctor of pharmacy, to include her insights into the industry that one might not observe from outside of it.

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  • 7 Steps to Get Off Sugar and Carbohydrates – by Susan Neal

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    We will not keep the steps a mystery; abbreviated, they are:

    1. decide to really do this thing
    2. get knowledge and support
    3. clean out that pantry/fridge/etc and put those things behind you
    4. buy in healthy foods while starving your candida
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    Particularly important amongst those are starving the candida (the fungus in your gut that is responsible for a lot of carb cravings, especially sugar and alcohol—which latter can be broken down easily into sugar), and changing the “how” of eating as well as the “what”; those are both things that are often overlooked in a lot of guides, but this one delivers well.

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  • Applesauce vs Cranberry Sauce – Which is Healthier?

    10almonds is reader-supported. We may, at no cost to you, receive a portion of sales if you purchase a product through a link in this article.

    Our Verdict

    When comparing applesauce to cranberry sauce, we picked the applesauce.

    Why?

    It mostly comes down to the fact that apples are sweeter than cranberries:

    In terms of macros, they are both equal on fiber (both languishing at a paltry 1.1g/100g), and/but cranberry sauce has 4x the carbs, of which, more than 3x the sugar. Simply, cranberry sauce recipes invariably have a lot of added sugar, while applesauce recipes don’t need that. So this is a huge relative win for applesauce (we say “relative” because it’s still not great, but cranberry sauce is far worse).

    In the category of vitamins, applesauce has more of vitamins B1, B2, B5, B6, B9, and C, while cranberry sauce has more of vitamins E, K, and choline. A more moderate win for applesauce this time.

    When it comes to minerals, applesauce has more calcium, copper, magnesium, phosphorus, and potassium, while cranberry sauce has more iron, manganese, and selenium. Another moderate win for applesauce.

    Since we’ve discussed relative amounts rather than actual quantities, it’s worth noting that neither sauce is a good source of vitamins or minerals, and neither are close to just eating the actual fruits. Just, cranberry sauce is the relatively more barren of the two.

    While cranberries famously have some UTI-fighting properties, you cannot usefully gain this benefit from a sauce that (with its very high sugar content and minimal fiber) actively feeds the very C. albicans you are likely trying to kill.

    All in all, a pitiful show of nutritional inadequacy from these two products today, but one is relatively less bad than the other, and that’s the applesauce.

    Want to learn more?

    You might like to read:

    From Apples to Bees, and High-Fructose Cs: Which Sugars Are Healthier, And Which Are Just The Same?

    Enjoy!

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  • This Is Your Brain on Food – by Dr. Uma Naidoo

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    “Diet will fix your brain” is a bold claim that often comes from wishful thinking and an optimistic place where anecdote is louder than evidence. But, diet does incontrovertibly also affect brain health. So, what does Dr. Naidoo bring to the table?

    The author is a Harvard-trained psychiatrist, a professional chef who graduated with her culinary school’s most coveted award, and a trained-and-certified nutritionist. Between those three qualifications, it’s safe to she knows her stuff when it comes to the niche that is nutritional psychiatry. And it shows.

    She takes us through the neurochemistry involved, what chemicals are consumed, made, affected, inhibited, upregulated, etc, what passes through the blood-brain barrier and what doesn’t, what part the gut really plays in its “second brain” role, and how we can leverage that—as well as mythbusting a lot of popular misconceptions about certain foods and moods.

    There’s hard science in here, but presented in quite a pop-science way, making for a very light yet informative read.

    Bottom line: if you’d like to better understand what your food is doing to your brain (and what it could be doing instead), then this is a top-tier book for you!

    Click here to check out This Is Your Brain On Food, and get to know yours!

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  • Intuitive Eating – by Evelyn Tribole and Elyse Resch

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    You may be given to wonder: if this is about intuitive eating, and an anti-diet approach, why a whole book?

    There’s a clue in the other part of the title: “4th Edition”.

    The reason there’s a 4th edition (and before it, a 3rd and 2nd edition) is because this book is very much full of science, and science begets more science, and the evidence just keeps on rolling in.

    While neither author is a doctor, each has a sizeable portion of the alphabet after their name (more than a lot of doctors), and this is an incredibly well-evidenced book.

    The basic premise from many studies is that restrictive dieting does not work well long-term for most people, and instead, better is to make use of our bodies’ own interoceptive feedback.

    You see, intuitive eating is not “eat randomly”. We do not call a person “intuitive” because they speak or act randomly, do we? Same with diet.

    Instead, the authors give us ten guiding principles (yes, still following the science) to allow us a consistent “finger on the pulse” of what our body has to say about what we have been eating, and what we should be eating.

    Bottom line: if you want to be a lot more in tune with your body and thus better able to nourish it the way it needs, this book is literally on the syllabus for many nutritional science classes, and will stand you in very good stead!

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