Battling Common Misconceptions about Sunscreen

It’s a summer’s day at the beach with the sun glaring down at you. In your bag, you reach for a bottle of sunscreen and liberally apply it to your body. Suddenly, you remember all the rumors you’ve heard about it and hesitate to continue applying. Sunscreen causes cancer. It is more harmful than direct sun exposure. It all works the same. These are all common myths about sunscreen, exacerbated by misinformation on social media. The truth is, these claims are scientifically disproven, and sunscreen is essential for sun protection.

Sunlight is necessary for life, but dangerous in excess. UV rays are classified into three types: UVA and UVB (which are dangerous), as well as UVC. UVC rays don’t reach the Earth’s surface, blocked by the Earth’s ozone layer. While UVB rays have higher energy levels than UVA rays, they typically only damage the outer layer of the skin, or epidermis, causing sunburn. UVA rays, on the other hand, have a longer wavelength, allowing them to penetrate deeper into the skin causing long term damage to cells. However, the skin also uses sunlight to help create Vitamin D, a supplement necessary for bone formation. During exposure to sunlight, UVB radiation is absorbed, converting 7-dehydrocholesterol, a side product made from the formation of cholesterol in the body, to previtamin D3, which isomerizes, or changes its structure, into Vitamin D.

 In the process, ultraviolet light may also cause major damage to the epidermis. Melanin is the pigment that determines skin complexion and protects the skin from UV rays, acting as an absorbent; it exists in two forms: eumelanin and pheomelanin. UV radiation is classified as a complete carcinogen, meaning it can act as both a tumor initiator and promoter. Tumor initiators covalently bond to DNA in the cell, changing them in a way that allows tumors to grow. Unlike initiators, promoters bind to receptors on the cell surface, altering gene expression, often stopping programmed cell death, which allows cancer to develop. It causes mutations by producing a reactive oxygen species in the skin, promoting the mispairing of highly susceptible nucleotides based on their position relative to other nucleotides. These changes to genes lead to cell mutations, which may cause the cell to rapidly divide, potentially leading to skin cancer. 

Skin cancer is by far the most common cancer found in humans, with over a million diagnosed a year. Roughly one in five Americans will develop skin cancer in their lifetime, accounting for nearly 15,000 deaths a year. The most common skin cancer is basal cell carcinoma, characterized by uncontrolled growth in the epidermis. Approximately 3.6 million cases are diagnosed annually, but it is rarely fatal. Melanoma, on the other hand, kills up to 8,000 people a year and is the most dangerous type of skin cancer. It develops from the melanin pigment and over 50 percent of the cases are invasive, meaning that they will penetrate further into the skin.

However, the majority of skin cancer can be prevented; 95 percent of malignant melanomas are caused by excessive sun damage. Using sun protection, such as sunscreen, is key to cancer prevention. Sunscreen comes in two main forms: physical and chemical blockers. Physical blockers, as the name suggests, physically prevent ultraviolet rays from entering the body, reflecting them away. They contain either zinc oxide or titanium dioxide, minerals ground into fine particles that sit on the skin’s surface, acting as a mirror. Both have very high refractive indexes, a measure determined by their ability to bend a light away, allowing them to be very effective. It may be even possible to see the flash of a camera reflected off skin applied with physical blockers. Chemical blockers, on the other hand, form a thin protective lining on the skin, preventing penetration. They absorb the UV rays, turning them into heat which is then released from the body. Chemical sunscreens typically include UV filters such as aminobenzoic acid, avobenzone, or oxybenzone. In this process, once UV hits the filter molecule, the molecule reaches an excited state, or is higher in energy. When it returns to the ground state, or lowest energy state, it releases heat energy with longer wavelengths, and thus lower energy. Chemical blockers absorb light at a lower energy level than most chemicals, contributing to its efficacy. The most infamous of these UV filters is oxybenzone due to concerns of it being a hormone disruptor. However, there has been no conclusive evidence that oxybenzone is harmful in humans. Despite this, use of oxybenzone has declined by more than half, only present in six percent of sunscreens in 2023. Oxybenzone has also been banned or restricted in many countries due to health concerns, as well as environmental effects, as it has been shown to create deformities in coral larvae. While it may be best to avoid sunscreens that contain oxybenzone as a precautionary measure, other sunscreens are completely safe. There have been conclusive studies demonstrating that sunscreen reduces photoaging and the risk of skin cancer by up to 40 percent as well as studies that disprove concerns about chemical absorption and endocrine disruption. 

Often, health issues thought to have been caused by sunscreen are actually due to the misuse of sunscreen. Sunscreen provides a false sense of security for many, believing that if applied, one will be completely protected from harm, prolonging the duration of their sun exposure. Underapplication and failure to reapply sunscreen are the main reasons they fail. The FDA recommends applying two milligrams of sunscreen per square centimeter of skin, and reapplying after two hours or right after water exposure, such as sweat or swimming. Additionally, sunscreen is still necessary on a cloudy day. Eighty percent of UV rays pass through clouds, making it still dangerous to be unprotected.

There are many preventive measures besides sunscreen that protect the skin as well. One way to do this is avoid a large amount of direct sun exposure in general. Seeking out shade, as well as wearing sun-protective clothing, reduces the risk of sunburn and skin cancer. Most sun-protective clothing is UPF 50 or higher, making it more effective than typical SPF sunscreens. However, if sun exposure is inevitable, sunscreen is essential, with the benefits outweighing any potential risks.