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If you are someone who loves skincare, you’ve probably heard that sunscreen is one of the most important steps in a routine, but why though? Simply speaking, sunscreens are creams or lotions that provide protection from the sun's harmful ultraviolet (UV) rays that cause skin cancer and premature aging (E. Richard, MD, 2022). This fact makes them a drug and a cosmetic in the United States because it moisturizes the skin and contains UV filters that can prevent skin cancer, AND wrinkles (double whammy)! 

Benefits of SPF For Your Skin Barrier

Without applying sunscreen, your skin will be exposed to the whole spectrum of UV rays, most importantly UVA and UVB. To remember the difference, think of them in terms of aging and burning: UVA affects aging (causing wrinkles) and UVB is what makes your skin burn. Even though you can't see them, they’re alllways there, yes, even on a cloudy day. This is because UVA rays work to damage the skin over time – not as immediate as the consequences of UVB, but just as harmful (Center for Disease Control, 2022).  

Our skin is our first line of defense on our body to protect from bacteria and microbes (E. Richard, MD, 2022). A healthy skin barrier is super important to keeping your general health in check. A weakened barrier allows for illnesses and discomfort in the body. For example, a cut or burn is a literal sign of a damaged skin barrier, and they get infected so easily when not taken care of properly. Prolonged exposure to the sun can damage your skin in the same way. Either immediately (sunburn) or slowly (skin cancer). We love a healthy body, and sunscreen works to make sure our body warrior is prepped for battle, aka the sun. 


How It Works

Those sunscreens you’re seeing probably have a number on it, which is something called a Sun Protection Factor, aka SPF. That number is a calculation that explains the amount of radiation that is blocked by the sun. It is recommended that you wear sunscreen with at least 30 SPF or higher (although there's arguably not much better protection past SPF 50, but that’s another story) to protect from skin cancer and premature aging. Whatever the number, it means that it will take 30 times longer for your skin to burn than if you were unprotected. This is measured either directly on human skin, or via instrumentation. As a researcher myself, I test sunscreen using a UV Transmittance Analyzer, by spreading a controlled amount of sunscreen onto a PMMA plate for exactly 60 seconds and exposing it to UV radiation to get a result (FDA, 2017).

What’s the relationship between broad spectrum and SPF?

Most likely a sunscreen will have the term “broad spectrum”, but what does that even mean? Well, remember UVA and UVB? That's the spectrum it's referencing. Sunscreens almost always protect against UVB, the one mostly responsible for burning, but not always UVA if only one active ingredient is in the formulation. Sunscreen formulators like myself tend to make sure a product is broad spectrum by mixing various UV filters (like titanium dioxide and zinc oxide) that work to protect against both UVA and UVB (AAD, 2023), so be sure to check for these ingredients in your sunscreen to be sure your sunscreen is “broad spectrum”. 

The Difference Between Inorganic and Organic Sunscreen

You might have heard of different types of sunscreens, like inorganic and organic. Many people think that the difference between them is whether or not they’re natural, like USDA organic on a food label, but that’s not why they are called that. In reality, the only difference is how the active ingredients work. 

  • Inorganic, or physical sunscreen (zinc oxide and titanium dioxide), works by physically scattering UV rays via reflection and absorption
  • Organic, or chemical sunscreens (homosalate, oxybenzone) work through a chemical reaction that absorbs the UV rays, preventing them from reaching the skin. 

Both of which are completely viable and safe options for sun protection (Skin Cancer Foundation, 2022). 

How is the FDA involved?

The Food and Drug Administration (FDA) is the final boss of the game called sunscreen. Since they are regulated as drugs, the FDA pays close attention to make sure that every sunscreen on the market does what it says, and is properly tested for SPF and safety. So don’t worry, if there's sunscreen on the shelf, it’s approved by the FDA and safe! 


How to find your SPF

Inorganic vs organic – is there one that’s better?

If you’re thinking about getting some SPF for yourself, definitely consider your skin type. 

Inorganic sunscreen tends to be a bit better for those whose skin are sensitive or easily irritated, and organic sunscreens might be better for oily or acne prone skin as it doesn't clog pores as easily, and is also more lightweight and easy to apply.. Organic sunscreens are also  more water resistant– good for those of you who love a good swim or workout!  And for those of us with darker skin, organic sunscreen blends wayyy easier than inorganic, because they tend to not leave a white cast. 

What Is The 2 Finger Rule?

A common method for proper coverage and protection in sunscreen application is the two finger method, which is applying a full amount of sunscreen onto your pointer and middle finger before applying. This is important because, like I mentioned earlier, SPF is tested using a PMMA plate, which must have exactly 2 milligrams of sunscreen per square centimeter. The two finger method mimics this to get the perfect layer of protection (Kuroda A, 2019). 

Sunscreens come in so many different forms. From lotions, to sprays, to makeup – there's a ton of ways to protect your skin. Find the kind that works best for you and try to stick to it daily! 

How to heal sun-damaged skin barrier

In the case that your skin is damaged by the sun, make sure to use  products that internally and externally soothe your skin. Externally, look for common soothing agents in skincare like aloe vera and colloidal oatmeal. Internally, the best vitamins and supplements for sun damage are chamomile tea, vitamins C, E, A, and D, as well as Omega-3 fatty acids as ingestible supplements can help with reducing inflammation and encourage collagen production (D. Bouilly‐Gauthier, 2010).  

Always Wear Protection! 

The moral of the story, we don’t like to tell you what to do, but we will say: wear. your. sunscreen. Even when you don’t feel like it, even if it's cloudy out. Your future self will thank you.  

If you enjoyed this journal, stay tuned to see more from us at MULTI! Be our healthy bestie and sign up for our DotCom, where we talk about topics like these and SO much more. We’d love to hear from you! 



Written by Alayna Bouie, BSPS, MSPS, founder of Shereen Cosmetics

Find her work here: Alayna BouieShereen Cosmetics






American Cancer Society. "Sunscreen and Sun Safety." 26 Jan. 2022, Accessed 29 Mar. 2023.

Centers for Disease Control and Prevention (CDC). "Sun Safety." 31 Jan. 2022, Accessed 29 Mar. 2023.

Skin Cancer Foundation. "Sunscreens Explained." n.d., Accessed 29 Mar. 2023.

Kuroda, A., et al. "Surface Structures of Cosmetic Standard Poly Methyl Methacrylate UV Evaluation Plates and their Influence on the in vitro Evaluation of UV Protection Abilities of Cosmetic Sunscreens." J Oleo Sci, vol. 68, no. 2, 2019, pp. 175-182, doi: 10.5650/jos.ess18207.

Bouilly-Gauthier, D., et al. "Clinical Evidence of Benefits of a Dietary Supplement Containing Probiotic and Carotenoids on Ultraviolet-Induced Skin Damage." British Journal of Dermatology, vol. 163, no. 3, 2010, pp. 536-543, doi: 10.1111/j.1365-2133.2010.09888.x.

H;, Cole C;Shyr T;Ou-Yang. “Metal Oxide Sunscreens Protect Skin by Absorption, Not by Reflection or Scattering.” Photodermatology, Photoimmunology & Photomedicine, U.S. National Library of Medicine, 

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