Efficacy and safety of using sunscreens for skin cancer prevention

The development of the first commercial sunscreen dates back to 1928 when the need for a safe and effective product to protect the skin from ultraviolet (UV) radiation was first raised. 

An article by Canadian authors titled "The efficacy and safety of sunscreen use for the prevention of skin cancer" (Megan Sander et al, 2020), published in the CMAJ (Canadian Medical Association Journal), provides data accumulated from 1984 to 2020 regarding the role of sunscreens in the prevalence of skin cancer. The article presents statistical data on over 80,000 cases of skin cancer registered annually in Canada. Sunscreens are considered indispensable for preventing skin photoaging and skin cancer. For instance, the Canadian Dermatology Association and the North American Academy of Dermatology strongly recommend the use of sunscreens.  

How do sunscreens work?

The goal of sunscreen is to block UV radiation. The wavelength of UV light is shorter than that of visible light. The shorter the wavelength, the higher the likelihood of biological damage. UV radiation is subdivided into:

•  Ultraviolet A1/A2 (UVA1/UVA2)
•  Ultraviolet B (UVB)
•  Ultraviolet C (UVC)

Sunscreens are active against UVA1, UVA2, and UVB radiation and may contain:

•  Chemical (organic) filters
•  Physical (inorganic) filters

Chemical filters, which absorb high-intensity UV radiation, consist of aromatic compounds such as:

•  Oxybenzone
•  Avobenzone
•  Octocrylene
•  Ecamsule

Absorption of UV radiation leads to the excitation of the molecules of these compounds. As a result, when the molecules return to their original state, the absorbed energy is transformed into lower-energy waves, such as infrared radiation.  

Physical filters reflect or scatter UV radiation from the skin surface. If the size of the physical particles is miniscule, the mechanism of action of physical filters is similar to that of chemical filters. Physical filters include:

•  Titanium dioxide
•  Zinc oxide

Efficacy of sunscreens in preventing photoaging and skin cancer

Numerous clinical studies since the 1980s have confirmed the effectiveness of using sunscreens. For example, regular use of sunscreen has shown a 40% reduction in the risk of developing squamous cell carcinomas in the study groups (Green A. et al, 1999). However, it did not affect the incidence of basal cell carcinomas. After a 15-year study, the group of participants who regularly used UV filters demonstrated a significant reduction in the risk of invasive melanoma. Another major Australian study (Thompson SC. et al, 1993) showed a significant reduction in the rate of actinic keratoses, the precursor to squamous cell carcinoma. Overall, the available evidence suggests that sunscreens do effectively prevent skin cancer.

Additional photoprotection measures

Additional photoprotection methods can be intended for both localized and general application. A particular interest lies in the group of antioxidants:

•  Vitamin C
•  Vitamin E
•  Selenium
•  Green tea polyphenols

Unfortunately, antioxidants have not yet been stabilized in sunscreen formulations to guarantee the preservation of their biological activity. Studies have found that sunscreens claiming antioxidant activity do not possess such properties (Ghazipura M. et al, 2017).

In addition to antioxidants, the following photoprotective agents for general use should be mentioned:

•  Niacinamide/nicotinamide
•  Polypodium leucotomos extract

Niacinamide, also known as nicotinamide, is the active form of niacin (vitamin B3). However, unlike niacin, it does not cause skin flushing. Niacinamide enhances DNA repair and reduces the formation of dimers in human keratinocytes, which contribute to actinic keratosis and nonmelanoma skin cancers.

Polypodium leucotomos extract is derived from a fern that grows in Central and South America. This substance is capable of increasing the minimal erythema dose of sun exposure without side effects. Additionally, the extract is beneficial for dermatological conditions induced by UV radiation, such as polymorphous light eruption and solar urticaria.

Therefore, sunscreens have significant potential, and the results of randomized controlled trials with long-term follow-up are compelling, demonstrating a reduced risk of squamous cell carcinoma and melanoma with the use of sunscreens.

How should UV filters be applied correctly?

How do sunscreens affect the environment?

Read about these topics in our article "How to Properly Use Sunscreens?"