Imagine stepping outside on a cloudy day, feeling confident that your skin is safe from the sun's rays simply because the sun is hidden behind a layer of clouds. This common belief can be misleading and potentially harmful. The truth is, even on those overcast days, up to 80% of the sun's ultraviolet (UV) rays can still reach your skin, so sunscreen is your skin's best friend, rain or shine.
Ultraviolet radiation is a form of electromagnetic radiation from the sun, classified into three types based on wavelength: UVA, UVB, and UVC. UVC rays are mostly absorbed by the Earth's ozone layer and do not reach the surface. However, UVA and UVB rays do penetrate the atmosphere. UVA rays, which make up 90-99% of the UV radiation reaching the Earth, are notorious for penetrating deep into the skin, causing premature aging and contributing to skin cancer. UVB rays, although less prevalent, are the main culprits behind sunburn and direct DNA damage, leading to skin cancer as well. This dual threat from UVA and UVB rays necessitates the use of broad-spectrum sunscreens that protect against both types of radiation.
The origins of sunscreen trace back to ancient civilizations. The Egyptians, for instance, used natural ingredients like rice bran and jasmine to shield their skin from the sun. Modern sunscreen formulations, however, began emerging in the 1930s. Pioneers like Eugene Schueller, the founder of L'Oréal, developed the first commercial sunscreens, followed by Franz Greiter, who was also credited for introducing the concept of Sun Protection Factor (SPF), a measurement of the efficacy of sunscreen against sun-induced skin erythema. SPF is defined as the ratio of the least amount of UV radiation required to produce minimal erythema on skin protected by sunscreen to the amount of energy required to produce the same erythema on unprotected skin.
Today's sunscreens come in various forms – lotions, sprays, gels, and sticks – and contain either physical or chemical ingredients. Physical sunscreens, such as those containing zinc oxide or titanium dioxide, act as barriers that reflect UV rays. Chemical sunscreens include compounds like avobenzone, octinoxate, and oxybenzone, which absorb UV rays and convert them to lower energy wavelengths.
Despite the advances in sunscreen technology, misconceptions about its use persist. Many people mistakenly associate UV exposure with temperature and cloud cover, leading to increased sunburn incidences on cooler, overcast days when they believe they are safe from UV rays. In reality, clouds only block a portion of UV rays, and sunburn can still occur. Ultraviolet rays peak between 10 AM and 3 PM, are more intense at higher altitudes and closer to the equator, and can be reflected by surfaces like sand, water, snow, and concrete, heightening the risk of sunburn. The risks of sun exposure extend far beyond the immediate discomfort of a sunburn. Long-term UV exposure accelerates skin aging, leading to wrinkles, leathery skin, and pigmentation changes. More critically, it suppresses the immune response in the skin, increasing the risk of pre-malignant and malignant conditions such as actinic keratosis and various forms of skin cancer, including basal cell carcinoma, squamous cell carcinoma, and melanoma.
To maximize the effectiveness of sunscreen, proper application is crucial. The standard amount tested is 2 mg/cm², which translates to about a shot glass full to cover an adult’s body. Yet, people typically use only a fraction of this amount, diminishing the protective benefits. Reapplication is equally important, ideally every two hours, or more frequently if swimming or sweating. Ensuring coverage of often-missed areas like the ears, neck, feet, and backs of the hands is also essential.
Regular, generous application of broad-spectrum sunscreen is a simple yet powerful tool in protecting your skin. So, next time you see clouds, remember that the sun’s rays are still in play, and your sunscreen is your winning move.
Hosna Akhgary is a BSc candidate at McGill University, majoring in Pharmacology.
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