In Canada, more than 80,000 cases of skin cancer are diagnosed every year. Because exposure to ultraviolet radiation is estimated to be associated with 80%–90% of skin cancers, the use of sunscreen — which blocks ultraviolet radiation — is promoted as an important means of preventing skin cancers, as well as sunburn and skin photoaging.
Use of sunscreen has been shown to reduce the incidence of both melanoma and nonmelanoma skin cancers. Both the Canadian Dermatology Association and the American Academy of Dermatology recommend the use of sunscreen for the prevention of skin cancer. Yet, since the development of the first commercial sunscreen in 1928, questions regarding the safety and efficacy of sunscreen have been raised, and more recently, the impact of sunscreens on the environment has become a cause for concern.
A review published in CMAJ Group summarizes evidence related to the effectiveness and harms of sunscreen to help physicians counsel their patients.
- Several well-conducted randomized controlled trials with long follow-up showed that sunscreen use reduces the risk of squamous cell and melanoma skin cancers.
- Commercial sunscreens protect against the skin-damaging effects of ultraviolet radiation through either chemical or physical ingredients.
- The Canadian Dermatology Association recommends the use of an adequate dose of a broad-spectrum sunscreen with a sun protection factor of at least 30 for most children and adults, as part of a comprehensive photoprotection strategy.
- Emerging evidence suggests that some chemical sunscreen ingredients are systemically absorbed, but the clinical importance of this remains unclear; further research is required to establish whether this results in harm.
- Ultraviolet filters found within chemical sunscreens may be harmful to the environment.
Exposure to ultraviolet radiation is directly harmful and has been associated with the development of skin cancers, which are common in Canada. High-quality evidence has shown that sunscreen reduces the risk of developing both melanoma and nonmelanoma skin cancer. Therefore, physicians should counsel patients on photoprotection strategies, including avoiding midday sun, seeking shade and wearing protective clothing, as well as using sunscreen if sun exposure cannot be avoided.
Presently, the Canadian Dermatology Association recommends the use of a broad-spectrum sunscreen with an SPF of at least 30 for people older than 6 months, for photoprotection. Low-quality evidence has shown that some chemical sunscreen ingredients are systemically absorbed and may be contributing to environmental damage; people who are concerned may consider using physical sunscreens as an alternative. Research on the safety and efficacy of established sunscreens and novel agents is ongoing.