How to correctly use sunscreen products?

In 2020 Canadian Medical Association Journal (CMAJ) published an article by Megan Sander et al. titled “The efficacy and safety of sunscreen use for the prevention of skin cancer.”  High risk of developing skin cancers such as melanoma, squamous cell carcinoma, and basal cell carcinoma is directly linked to ultraviolet (UV) radiation. One of the clinically proven effective methods to prevent skin cancer is the use of sunscreen products.

Recommendations for using sunscreen lotion for adults and children

The American Academy of Dermatology recommends regular use of sunscreen with SPF 30 (sun protection factor) or higher for individuals with any skin type. The Canadian Dermatology Association recommends using sunscreen with an SPF index of at least 30 for children over 6 months old and for adults. Using products with SPF 100 is significantly more effective than SPF 50 for preventing sunburn at the beach and high-altitude resorts.

The Canadian Ministry of Health does not recommend using sunscreen products on children under 6 months old. These restrictions are due to the risk of increased absorption of sunscreen ingredients because of the high ratio of the body's surface area to volume and the thin layer of epidermis in small children. The primary method of protecting infants' skin is to use protective clothing. Experts recommend washing off sunscreen from a child's skin as soon as it is no longer needed. Children are advised to use sunscreen products with physical agents as opposed to chemical ones.

Chemical filters include aromatic compounds that transform ultraviolet into lower-energy waves: oxybenzone, avobenzone, octocrylene, and ecamsule.

Physical filters like titanium dioxide and zinc oxide reflect or scatter UV radiation away from the skin.

How to properly apply sunscreen lotion

Consumers often apply sunscreen lotion in insufficient amounts, leading to only 20%-50% of the recommended protection. Using a lotion with a higher SPF compensates for inadequate application. The term "apply sunscreen generously" is the most appropriate. While sunscreen products' labels recommend applying the lotion 15-30 minutes before going outside, recent research has shown that SPF protection takes effect immediately after application. However, if water resistance is needed, one should wait for 15-30 minutes.

Recent studies (Bodekær M. et al, 2012) have shown that sunscreen remains effective on the skin for 8 hours after one application. Reapplying the lotion every 2-3 hours is not necessary even during increased activity. For swimming and increased sweating, it is recommended to use water-resistant products with SPF 40 or higher. Reapplication of SPF products is advised when:

•  Removing the sunscreen product
•  Experiencing increased sweating
•  Engaging in water activities
•  Rubbing against clothing
•  Experiencing sand exfoliation

The advantage of using creams over sprays includes the following:

•  Spray products dry quickly after application to the skin, making it difficult to assess evenness of application
•  Potential risks associated with inhaling SPF aerosols are not fully understood.

Side effects of using spf products

The most common side effects when using SPF products are subjective irritations, such as tingling or burning sensations. However, sometimes more serious undesirable complications can occur, including:

•  Allergic contact dermatitis
•  Photoallergic contact dermatitis
•  Comedogenicity (cosmetic products' property to clog pores)

The following components are the most frequent allergens in such products:

•  Octocrylene
•  Oxybenzone
•  Octylmethoxycinnamate

Absorption of sunscreen components

The Food and Drug Administration (FDA) published data on the systemic absorption of four sunscreen components in humans (Matta MK, 2019):

•  Oxybenzone
•  Avobenzone
•  Octocrylene
•  Ecamsule

Researchers also noted a prolonged half-life for each of these ingredients and suggested that regular use of sunscreen could lead to the accumulation of undesirable substances in the body (Califf RM, 2019). Despite these findings, researchers still encouraged the use of sunscreens, as most people use much less sunscreen than the amounts used in the study group, and the clinical significance of the absorption of these substances has not yet been determined.

Sunscreen products with physical filters (titanium dioxide and zinc oxide) behave differently and do not absorb systemically. For example, only 0.03% of zinc nanoparticles penetrate the uppermost layer of the skin's stratum corneum, with none detected in the lower layers. Historically, creams with physical filters were less appealing cosmetically because they left a white residue. However, modern advances in cosmetics have led to the production of sunscreens with micronized physical filters, making them more attractive.

Impact of sunscreens on the environment

Recent studies have confirmed that sunscreen ingredients are found in various water sources and persist despite wastewater treatment. Sunscreen filters have also been detected in tissues of different fish, indicating the occurrence of bioaccumulation and biomagnification (Schneider SL, 2019).

Research on coral reefs has shown that oxybenzone affects coral fish larvae and may be responsible for coral bleaching. As a result, in some jurisdictions, the use of oxybenzone and octinoxate is prohibited (Ouchene L, 2019).

Conclusion

The impact of UV radiation is undoubtedly associated with the development of skin cancer. Numerous clinical studies have demonstrated the role of sunscreen products in reducing the risk of both melanoma and non-melanoma skin cancers.

Medical professionals should advise patients on photoprotection strategies, which include:

•  Avoiding midday sun exposure
•  Seeking shade
•  Wearing protective clothing
•  Using sunscreen with an SPF of at least 30 for individuals over 6 months old