How Do Sunscreens Work?

A no-nonsense guide to SPF

To understand how sunblock works, we first need to talk about ultraviolet radiation. There are three types of UV rays on the spectrum but the two most important are UVA and UVB Rays. UVC is the third type of ray, but it does not penetrate the ozone layer.

UV rays are first and foremost carcinogens (cancer causing), but they also contribute to skin aging and dark spots. Despite myths about suntanning to prevent sunburns, or our desire to be have glowing, bronzy skin, there is no safe amount of sun exposure (I know, it sucks!). Tans – or worse, sunburns – always cause damage to our skin.

Here is the breakdown

UVA rays are longer and less intense rays of energy. UVB rays are shorter and more intense. UVB rays don’t penetrate as deeply into the skin but they are most associated with a sunburn and skin cancer. UVA rays are most associated with skin aging and wrinkles and this is because they penetrate the dermis, or the layer of the skin that produces fibers like collagen and elastin, which support skin structure. Damage to collagen and elastin or low production are what causes wrinkles and fine lines, and also why we lose that bouncy, youthful skin as we age.

So now that we have a basic understanding of UVA and UVB rays, how do sunscreens protect us?

Graph UVA, UVB, UVC Rays.

Firstly, there are two types of sunscreen on the market: mineral and chemical.

Secondly, one is not better than the other.

How do chemical (organic) sunscreens work?

Organic sunscreens are not to be confused with “organic” products. This is purely a class of molecules in chemistry, and these sunscreens are not shown to be better than physical sunscreens. Chemical sunscreens work to block the sun by absorbing harmful UV rays and converting that energy to heat that is then released off the skin.

Sunscreens primarily block UVB rays. In the United States, purchasing SPF that says “Broad-spectrum” will protect against both UVA and UVB. To be clear, you need protection from both types of ultraviolet radiation and broad-spectrum SPF 30 or higher is recommended by physicians and dermatologists. 

Chemical sunscreens, also known as organic sunscreens, are usually a combination of chemical and mineral ingredients. They are good at protecting us against UVB. Avobenzone, sometimes listed as octinoxate, is a common ingredient in these sunscreens, and has been shown to be effective and safe on the skin.

How do physical (inorganic) sunscreens work?

Experts used to believe that inorganic sunscreens worked by “reflecting” UV Rays, but we know now that this isn’t exactly the case and they work by both reflecting and absorbing UV rays. They are just not as good at absorbing the UV rays as chemical sunscreens.

Zinc and titanium dioxide are the primary ingredients in physical sunscreens, also called mineral sunscreens, and dermatologists agree that they are better for sensitive or irritate skin.

Sunscreens can reflect and absorb UVA and UVB rays.

How much sun protection do we need?

If you have skin, sunscreen should be worn every day of the year – yes, even in the winter! Since other skin care products, like retinols and chemical or physical exfoliants, sensitize the skin, it can be even more important to use sunscreen every day.

There is no universal measure of how effective sunscreens are. The United States uses SPF, or sun protection factor, which describes how long you can stay in the sun and not experience sun damage. An SPF 15 means you can have sun exposure for 15 times longer than you would without the use of an SPF, but again, no sunscreen below SPF 30 is recommended by experts.

Another common type of system is the PA+ system seen in Korean brands, since this is the measurement system in many eastern countries.

What are the best sunscreens?

The best sunscreen will be broad spectrum and over SPF 30 or PA+++, and one that you will wear every single day.

Yep, that’s it. The best sunscreen is FDA approved (here in the US) and one that you will wear every single day. Regardless of the sunscreen type or brand, consistent use of an SPF is the best defense to protect against skin cancers, breakdown of collagen and elastin, as well as overall skin aging.

That said, some sunscreens are just formulated for a nicer experience, and they can be more luxurious than an SPF purchased at the drugstore. I have my favorites, but the two I always have on hand are Missha All Around Safe Block Essence (this is my favorite because it has no smell and feels silky) and Aveeno Positively Radiant Daily Sunscreen because they feel like lightweight moisturizers, are affordable for every day use, and effective when you are inside working and not directly exposed to the sun.


Please feel free to purchase any of these products from Amazon using the links above, but be aware they are affiliate links. All monies made supports my espresso addiction and product reviews.


Cerave Resurfacing Retinol Serum Review

Product Review

Resurfacing Retinol Serum (30 ml/1 oz, $16.99)

Skincare doesn’t have to be expensive and one of the best affordable brands is Cerave. I have reviewed quite a few Cerave products, so I very much have my favorites, but this product is one of my favorites from the brand.

The Cerave Resurfacing Retinol Serum is an effective retinol product for seasoned retinol users. It’s a potent retinol serum from the #1 recommended brand by dermatologists and is also largely considered to be a brand that produces the most affordable and efficacious products on the in the skincare industry.

This serum is a great affordable retinol serum if you are looking for a product $20.00 and under. 1 oz of product will usually run you about $17.00, but you can find it even cheaper when retailers price cut, for example, it’s currently $11.50 on if you sign up for their subscribe and save program; otherwise its $12.10, which is still a steal!

This serum is honestly one of the most affordable and effective retinol products that I have used. That’s to say, it’s not exactly the best – that honor goes to Skinceuticals 1.0 Retinol Cream. I talk about that product in my article Best Retinol Serums where I outline 5 great retinol serum options with different price points. The Skinceuticals retinol cream is the priciest of the 5 recommendations, but it’s worth it.

The nice thing about this retinol in particular is that is that is has encapsulated retinol. Encapsulated retinol offers a slower release of the retinol, so it’s not immediately active on the skin, instead releasing over time, so it’s a great option for  those with dry and sensitive skin (like me!).

This serum is fragrance-free and has additional ingredients to promote skin barrier health, like niacinamide and ceramides. Ceramides help build the skin cell barrier (more on ingredients and their benefits in another post) and niacinamide helps control sebum production and maintain the skin barrier.

This serum also contains hyaluronic acid to help hydrate the skin. As a note, hyaluronic acid is in virtually every skincare product these days, but it isn’t necessary in a skincare routine. If your skin can handle it, it’s a wonderful ingredient for dry and aging skin that helps the skin look more radiant and plumper.

As far as the experience with the product? It’s not luxurious to be honest. That’s not saying is not a nice product, but it has more of a gel texture than a thinner, lighter serum that has a texture more similar to a true serum. If you struggle with acne prone or oily skin this product is a good option because it’s not heavy.


  • 3 Essential ceramides
  • Niacinimide
  • Hyalronic acid
  • Encapsulated Retinol
Show ceramides


  • Fragrance free
  • Paraben free
  • Affordable
  • Evens skin tone and texture
  • Strengthens skin barrier
  • Reduces wrinkles

Overall, this product is a great option for anyone looking add a retinol into their nighttime routine. Dermatologists recommend starting out 1x per week and increasing usage to 4 – 7 times per week if your skin can handle it, so that you are optimizing the benefits of over-the-counter retinol.


Please note that all links are Amazon affiliate links. All monies made will support this blog and product reviews.

Best Retinol Serums

Retinols and retinoids are the holy grail and gold standard of the skincare world.

Retinols and retinoids, also known as vitamin A, are often used interchangeably, and are truly the closest thing we have to The Fountain of Youth. When used appropriately, they are the most effective active skincare ingredient on the market to boost collagen and elastin, proteins that start to decline in production in most people around the age of 26 years old.

With everyday use of an SPF, 50 plus years of studies have proven that retinols delay the aging by increasing skin cell turnover and stimulating the production of collagen, resulting in improvement of the appearance of fine lines and wrinkles, as well as minimizing the appearance of pores and dark spots. Retinoids are the purest form of vitamin A. Retinols and retinals are less potent derivates that are approved by FDA for over-the-counter us. They are found in most skincare products advertising retinol as their main active ingredient.

So, without further ado, I’ve listed 5 effective retinol serums from which I’ve seen great results.

1. Best Budget Friendly

Cerave is one of the most trusted and recommended brands among dermatologists. Their Resurfacing Retinol Serum is a great pick if you are want to start a retinoid, but don’t want to spend a ton of money. This is also a great product for those with dry and sensitive skin, since it’s formulated with encapsulated retinol.

Traditional retinols and retinoids start working immediately upon application. Encapsulated retinol is released after application in a time-dependent manner. The retinol will active slowly over-time, so it’s a gentler option than other forms of vitamin A. This serum also contains ceramides and niacinamide, which help heal inflammation and damage to the skin barrier. You can read my full review here.

2. Best For Dry Skin

Naturium Retinol Complex Serum (30ml/1 oz, $20.00)

Naturium’s Retinol Complex Serum is the best I have found for sensitive and dry skin. This serum, like The Cerave Resurfacing Retinol Serum contains encapsulated retinol, which makes it perfect for dry and sensitive skin types. The Retinol Complex Serum’s texture is more akin to a very light moisturizer than a traditional serum. The thicker texture allows the active ingredients to penetrate slower into the skin, creating a more gentle retinol product.

The Retinol Complex is also formulated with Bakuchiol, a plant-derived alternative to retinol. While it has not been shown to be as effective as a true retinol, it has shown promising results in reducing wrinkles. This serum is also formulated with vitamin E, an antioxidant, as well as hyaluronic acid to help promote hydration in the skin.

3. Best Retinol Serum

Murad is a well known cosmeceutical skincare line, and their Retinol Youth Renewal Serum is a wonderful option if you want a more luxurious experience from you retinol serum, but still want efficacy. The serum has a heavy consistency that your average serum and could double as a moisturizer for oily skin types.

The serum is formulated with 3 different kinds of retinol, and because of this I noticed results quicker than with other products. It also contains hyaluronic acid to support hydration in the skin, and ceramides to improve skin barrier texture and function.

4. Best Drugstore

When it comes to the best bang for your buck, you can’t beat Differin Gel. As a side note, this product is HSA and FSA (in the US) eligible so you can reimburse yourself through your health savings plan.Once available by prescription only to treat acne, The FDA approved Adapalene Gel .1% for over-the-counter use in the US in 2016.

The light gel texture is not the most glamorous, but it contains the active form of retinol, retinoid, and helps reduce dark spots, acne, and improves collagen production.  Due to the potency, it’s recommended that a new retinoid or retinol user should start by layering the gel over their moisturizer 1–2 times per week until your skin has a tolerance.

When it comes to the best bang for your buck, you can’t beat Differin Gel. As a side note, this product is HSA and FSA (in the US) eligible so you can reimburse yourself through your health savings plan.Once available by prescription only to treat acne, The FDA approved Adapalene Gel .1% for over-the-counter use in the US in 2016.

5. Best Overall

Cerave Resurfacing Retinol Serum
Skinceuticals Retinol Cream 1.0%, 0.5%, and 0.3%. Acne Treatment Differin Gel. Adapalene Gel.

As far as retinol cream goes, you can’t beat SkinCeutical’s retinol creams. Dermatologists consider Skinceuticals the gold standard when it comes to over the counter skincare. The Skinceuticals 1.0% Pure Retinol Cream is offered in many dermatology offices as an alternative to Tretinoin, a prescription retinoid.

The 1.0 Retinol Cream is a lightweight cream that can be used on its own or layered with your normal moisturizer. If you are new to retinoids or have sensitive skin and find the 1.0% too potent, it’s also available in .3% and .5%.


Regardless of your price point, there are plenty of great options when it comes to choosing a retinol that works for your skin type and concerns. If you haven’t tried one, I highly recommend starting one; if you are a seasoned retinol user, I hope you give one of these products a try. The retinols were highly effective and don’t add anytime to your nightly routine! These can all be found on or purchased directly from the brand.


Please note that all links are Amazon affiliate links. All monies made will support this blog and product reviews.

Welcome to Books in the Attic Blog

Photo by Jessica Lewis Creative on

Welcome, here on this blog we love all things skincare and beauty.

A little about me.

I’m a twenty-something writer based in Oregon, USA, who received my Bachelor of Arts in Spanish with a minor in linguistics after abandoning my chemistry degree my senior year. This left me with all my chemistry and biology textbooks – and knowledge – in my proverbial attic, and now I’ve turned all this information on my second love of beauty and skincare.

Beauty and skincare is the main focus of the blog, but I do also write on topics like finance. I believe financial well-being is dependent on overall wellness, and is therefore unavoidable when discussing beauty and health.

While my second love is skincare, my first love is storytelling. I write fiction as a hobby and hope to have my stories told and published sometime in my lifetime.

I hope you enjoy, and if this sounds like content you would like to support, please consider subscribing. Happy reading!

All my best,