Introduction: 

Whether it is eating outside during an overcast day or swimming at the beach, the Sun’s ultraviolet (UV) A and B rays will always manage to find a way into the skin. For some, the effect comes in the form of a nice tan, while for others painful, red, and sometimes swollen sunburns can develop. However, just because a tan is slightly more appealing and comfortable, doesn’t mean that it is any less damaging than a sunburn. Both forms are considered harmful and indicate skin damage from the Sun. If this damage is repeated overtime without proper protection, the risk of skin cancer, specifically melanoma, significantly increases. 

Importance of sunscreen:

It is estimated by the American Cancer Society that there is a 3% lifetime risk of getting skin cancer or melanoma, with some differences depending on risk factors such as age and skin color. There will be approximately 104,960 new melanomas diagnosed in 2025, making melanoma the 5th most common cancer diagnosis in the United States. The most common and well known cause of melanoma is UV light exposure. UVB and UVA rays, both of which are released from the sun, are known to cause skin cancer through a process called  photocarcinogenesis. 

Photocarcinogenesis is the process in which UV rays damage DNA, leading to mutations in the structure. Cells with the damaged DNA will be mutated, replicating rapidly and spreading to other regions of the body. According to the study Mechanism of UV-related carcinogenesis and its contribution to nevi/melanoma in the journal Expert Review of Dermatology, UVB and UVA rays are also responsible for photoaging, a process where repeated and extended exposure to rays causes damage to the DNA in the deeper layers of the skin, leading to aging effects. Beyond the cosmetic effects, the skin acts as the first physical barrier against harmful bacteria, and taking care of it is an important step in preventing infection or disease. 

What is sunscreen? 

To protect and care for our largest organ, sunscreen is vital. According to Sunscreen Application, Safety, and Sun Protection: The Evidence, the effectiveness of sunscreen is determined by its sun protection factor (SPF). The United States FDA (Food and Drug Administration) defines SPF as a measure that compares the amount of solar energy (UV radiation) needed to cause sunburn on protected skin against the amount needed to cause sunburn on unprotected skin. Generally, the higher the SPF, the stronger the protection, be it by physical or chemical blockers. For example, the study High SPF Sunscreen Provides Significant Clinical Benefit in Actual Use Conditions: SPF 100+ is More Effective Than SPF 50+ utilized a split-face, randomized, double-blind clinical trial where SPF 50+ was applied to one side of the face and SPF 100+ to the other side. They found that the SPF 100+ side showed significantly less sunburn after sun exposure. Thus, this study concluded that SPF 100+ provided significantly greater protection against sunburn than SPF 50+.

However, SPF is not the only factor that contributes to a well-rounded sunscreen. The American Academy of Dermatology recommends using a sunscreen that contains an SPF of above 30, is broad spectrum, and is water resistant. The FDA defines broad spectrum as a sunscreen that protects against both forms of UV radiation, UVA and UVB rays. Non-broad-spectrum sunscreen only protects against UVB rays, which is risky as UVA rays contribute to skin aging and skin cancer. Additionally, water resistance is important since it will still protect the skin from the sun when an individual is in or exposed to water.

Which should I use?

Despite all this information, some questions remain unanswered. Which type of sunscreen to use? How much? How often? 

The brand of sunscreen does not matter. Instead, focus on the ingredients. According to UC Davis Health, the two main types of ingredients can be categorized into physical and chemical blockers. Physical blockers include zinc oxide and titanium dioxide. Physical blockers are considered to be more effective, having a broader coverage and working immediately after applying. On the other hand, chemical blockers include avobenzone and oxybenzone. These molecules need to be absorbed into the skin where they can then absorb and release UVA and UVB rays, preventing their impact on the skin cells. 

Unfortunately, if you are looking to go for a swim in an ocean or stream, oxybenzone may not be a good choice as it is a known toxin for coral reefs. Oxybenzone can wash off into the water and accumulate in coral tissues, which causes bleaching, DNA damage, and deformities. It also has impacts on other marine life, namely green algae, sea urchins, and reef fish. The oxybenzone impacts photosynthesis processes and can lead to hormonal imbalances in marine life, impacting their fertility and immune systems. This can greatly impact coral reef ecological diversity, leading to increased global reef loss and the devastation of local ecosystems. This necessitates a careful selection of sunscreen, ensuring it doesn’t cause damage to the marine environment while still protecting your skin.
Regarding the amount and frequency of sunscreen use, UC Davis Health recommends that adults use one ounce of sunscreen for each area exposed to the sun, while children are recommended to use about half that amount. For both adults and children, sunscreen should be constantly reapplied every two hours for proper protection. The American Cancer Society states that early childhood exposure to UVA and UVB rays can contribute to an increased risk of skin cancer. This makes it incredibly important to start safe sun practices early and maintain these practices whenever you are in the sun. 

Sunscreens that are both effective and coral-reef safe: 

1. Badger Reef Safe Sunscreen, SPF 40

2. Best Reef Safe Sunscreen for Sensitive Skin, SPF 50

3. Raw Elements SPF 50 Mineral Sunscreen Spray

4. ThinkBaby SPF 50+ Baby Sunscreen 

5. Thrive Natural Body Mineral Sunscreen, SPF 50

Lillia Edalat

Psychobiology B.S. ‘28

Leewon Koo

Biology B.S. ‘26