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As the summer returns and we start spending more time outdoors this is your yearly sunscreen reminder! Using sunscreen to protect your skin is necessary year round but with more hours of sunlight and warmer weather, using appropriate sunscreen and skin protection becomes extra important in the summer. Sunscreen gets a lots of buzz (and rightly so!) so while we imagine this is not your first time hearing about sunscreen, we’ll be going through some of the basics of how sunscreen works, why it’s so essential in staying healthy long term, and some good sunscreen options!

Why is sunscreen important?

Sunscreen’s job is simple, to protect the skin from ultraviolet light generated by the sun that penetrates the atmosphere, the clouds, and ultimately, our skin. Ultraviolet light describes radiation produced by the sun that is a shorter wavelength than the light humans see. And even though we cannot see it, UV light is definitely still there! UV radiation makes up approximately 10% of the light produced by the sun and within the 10 nanometer to 400 nanometer wavelength spectrum of UV light, UV light can be further broken down into the three sub-bands of UV-A, UV-B, and UV-C light.[1] These classifications describe UV radiation of different wavelengths with differing properties and effects on the skin. With the shortest wavelength, UV-C light does not make it past the earth’s atmosphere; however, UV-B and UV-A light both reach the earth’s surface. UV-B light reaches the outer skin layers, the epidermis, and UV-A light reaches all the way to the deeper skin layer, the dermis.

As UV-A and UV-B reach different types of cells within the skin, they have different effects on our health. UV-B light reaching the epidermis is needed for the synthesis of Vitamin D and 10-15 minutes of sun exposure, 2-3 times a week is enough to produce the vitamin D your body needs.[3] While direct UV-B exposure is beneficial in small amounts, UV-B radiation also damages the epidermis. UV-B radiation causes inflammation within the epidermis, inducing a cascade of cytokines, vasoactive and neuroactive mediators in the skin that together result in an inflammatory response and causes “sunburn”. If the dose of UV exceeds a threshold damage response, keratinocytes activate apoptotic pathways and die.[4] UV-B also damages DNA and alters DNA processing systems within the cell, culminating in changes that lead to skin cancer. UV-A radiation that penetrates further into the dermis also causes inflammation and generates Reactive Oxygen Species  that in turn perpetuate cellular damage. These cellular changes are reflected in visible changes such as irritation, changes in color, loss or elasticity of skin, and eventually the development of skin cancer.

Changes in your skin can be visible immediately after too much sun exposure in the form of sunburns or blisters or can appear years later as early aging or skin cancer. Many other factors such as family history and exposure to additional toxins play a role in the development of skin cancer but protecting yourself from UV light is a highly effective way to take skin cancer prevention into your own hands. Using appropriate protection from UV light also prevents loss of skin elasticity and the fine lines and wrinkles that accompany loss of elasticity.

How does sunscreen work? Why are there so many types of sunscreen!

Selecting the right type of sunscreen can seem like an impossible task given endless options and overwhelming product-specific marketing. The two primary types of sunscreen are chemical and mineral sunscreens with the most effective forms of sunscreen using active ingredients from one or both of these categories.

Chemical Sunscreen

Chemical sunscreens absorb UV-A and UV-B light, transforming the chemical structure of the active ingredients and releasing energy from this transformation as non-damaging heat. Active ingredients in this category of sunscreen include oxybenzone, avobenzone, octisalate, octocrylene, homosalate, and octinoxate. These chemicals are referred to as “organic chemicals” in that they are carbon-based, a different organic than food or produce organic! These sunscreens are absorbed by your skin so they leave less of a white cast; however, they become effective 15 – 20 minutes after you put them on because of the time needed to absorb.[8]


Mineral sunscreen contains titanium dioxide and/or zinc oxide. Physical sunscreen reflects UV light in the way that clothing or an umbrella does. Mineral sunscreens are made up of particles that sit on top of your skin and block UV-A and UV-B radiation from entering the epidermis. Because these sunscreens work as a barrier they are effective immediately but may leave more of a white cast than chemical sunscreen.

Additional Active Ingredients

Many sunscreens include additional active ingredients that do not block UV light but protect against damage caused by UV light.  These are ingredients such as as vitamin C, vitamin E, silymarin, and green tea polyphenols that function as antioxidants to prevent cellular damage from reactive oxygen species. Reactive oxygen species are neutralized by antioxidants found naturally within the body, such as superoxide dismutase and catalase; however, these enzymes can become saturated within an overproduction of reactive oxygen species, resulting in a deficiency of antioxidants and damage to proteins and DNA. Topical antioxidants function from within the cell to decrease the shortage of antioxidants and can remain active for several days after application.[9]


SPF is a measurement that reflects the percentage of UV-A and UV-B light that a given sunscreen protects against. A SPF 15 sunscreen blocks 93% of UVB radiation, and SPF 30 blocks 97%. After that, the difference in protection is small. SPF 50 blocks 98%, and SPF 100 stops 99% of UVB rays from reaching your skin. Any sunscreen SPF  30 or above is a great option and selecting SPF 100 does not necessarily mean better coverage all the time due to the limitations of studying SPF with changing light intensity and other complicating factors. What is more important than the highest SPF available is consistently using and reapplying sunscreen every two hours while in the sun.


“Broad Spectrum” sunscreen refers to a sunscreen’s ability to protected against both UV-A and UV-B light. These can be chemical or mineral sunscreens and make sure to select broad spectrum options!


What should I be thinking about in choosing + using sunscreen?

Our recommendation is choosing a chemical and/or physical sunscreen that is broad-spectrum, SPF 30 (or above) and can be easily reapplied throughout the day! Reapply sunscreen every 2-3 hours and below are some additional considerations in making sure you stay protected against the sun!

Remember to apply on highly exposed areas such as ears, hands, tops of feet, back of the neck, and lips! Using sun protective clothing and hats can provide additional sun protection.

For Boating and Swimming

No sunscreen is truly waterproof but some are more water-resistant than others! Sunscreens used to be labeled as waterproof if they would remain effective for a period of time when swimming or sweating, but in a 2011 announcement, the FDA determined this was misleading and changed the sunscreen label requirements from waterproof to water-resistant where applicable.[10] Water-resistant sunscreens are required to be tested according to the FDA’s SPF test procedure. Sunscreens can be water-resistant for up to 40 minutes or 80 minutes, and this rating must be stated on the label. Sunscreen labels must also state when users should reapply water-resistant sunscreen for the most effective sun protection when swimming or sweating.

When swimming or boating, water resistant sunscreen can be helpful but the most important thing to keep in mind is consistently reapplying sunscreen as it will wash off if you’re in water or being splashed with water. Being on the water also means UV light reflecting off of the water so make sure to cover your entire body in sunscreen, even areas like under your chin that may not be directly exposed from above!

For Hiking

If you spend a lot of time outdoors walking or hiking, you’ll want to make sure you have good sun protection! Even if you’re outdoors in covered/forested areas it’s a good idea to wear sunscreen as UV light filters through tree and cloud cover. If you’re sweating a lot, selecting a water-resistant sunscreen as described above can be helpful and as always remember to bring sunscreen along with you and reapply!

Face vs Body sunscreen

Many sunscreens are marketed as face sunscreen or body sunscreen but ultimately sunscreen in sunscreen! People may choose to use different sunscreen on their face if they find some sunscreen makes their eyes sting, they are looking for more sheer coverage on their face, or they want to use sunscreen with additional antioxidants or anti-inflammatory ingredients on their face. If your body is covered with clothing and your face is more exposed to sun throughout the day you may find yourself reapplying on your face more frequently but many sunscreens work great for both your face and body! Additional things to consider are that face sunscreens often come in smaller more portable sizes and frequently have a higher price point.


Sunscreen Options

All around best options!

Water-resistant options!

Water resistant options for boating, swimming, sweaty sports! These options last longer than most in the water but no sunscreen is truly waterproof so remember to reapply every 1- 2 hours!

Options for Acne-Prone Skin!

For acne-prone skin the most important part of selecting sunscreen is choosing sunscreens without comedogenic ingredients. The most common comedogenic ingredients in sunscreen are coconut oil, shea butter, cocoa butter, beeswax, argan oil, stearic acid, squalene oil (squalane oil is great though!), and palm oil.

Options for Lips!

Lips can easily get sunburned and develop skin cancer! Regular sunscreen can be used on the lips but often rubs off more easily than lip protection + lip balms made specifically for lip sun protection. A lot of lip balms have great sun protection, some of our favorites below.


     Juli Brown, Idara Ndon

          Brown Medical Students


[1] ​​Narayanan DL, Saladi RN, Fox JL. Ultraviolet radiation and skin cancer. Int J Dermatol. 2010 Sep;49(9):978-86. doi: 10.1111/j.1365-4632.2010.04474.x. PMID: 20883261.


[4] D’Orazio J, Jarrett S, Amaro-Ortiz A, Scott T. UV radiation and the skin. Int J Mol Sci. 2013;14(6):12222-12248. Published 2013 Jun 7. doi:10.3390/ijms140612222

[8] Gabros S, Nessel TA, Zito PM. Sunscreens And Photoprotection. [Updated 2021 Nov 15]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from:

[9]Gabros et al.