Updated: Jan 19
Exposure to sunlight is important for lots of reasons, like the bio synthesis of vitamin D, and the regulation of the biological circadian rhythms. However, overexposure might lead to burns, skin irritation, and even skin cancer. As a result, people are heading towards the use of sunscreens, so what are sunscreens? How do they work? And are they safe to be used? Let’s find out…
Sunscreen, also known as Sunblock or Suntan Lotion, is a lotion, spray, gel, foam (such as an expanded foam lotion or whipped lotion), stick or other tropical product that absorbs or reflects some of the sun’s ultraviolet (UV) radiation and thus helps protect against its harmful effects. Diligent use of sunscreen can also help to slow or temporarily prevent the development of wrinkles, dark spots and sagging skin. (1)
Figure 1. Multiple pharmaceutical forms of sunscreens (2)
What types of sunscreen are there?
There are many types of sunscreens available. Sunscreens work because they contain filters that reflect, scatter, or absorb UV radiation that otherwise would reach your skin. There are two main types of sunscreens available,
separated into “organic filters” (aka chemical sunscreens) and “inorganic filters” (aka physical sunscreens).
1- Chemical sunscreens (organic filters):
Organic filters such as oxybenzone, avobenzone, and octocryle absorb UV radiation and convert it into a small amount of heat. Oxybenzone and avobenzone are relatively good filters for UVA radiation; however, they may be paired with other agents such as octocrylene, homosalate, and octisalate to stabilize them and provide UVB protection.
2- Physical sunscreens (inorganic filters):
Mineral compounds such as zinc oxide and titanium dioxide that theoretically work by reflecting and/or scattering UV light to protect your skin. These sunscreens tend to offer more broad-spectrum protection against both UVA and UVB light. They also tend to be the formulations used in children’s sunscreens, as they are easier on sensitive skin. (3)
Figure 2. Differences between physical and chemical sunscreens (4)
When we look at sunscreens, we notice the abbreviation SPF, so what does it stand for?
SPF stands for Sun Protection Factor, which also plays an important role as anti-pollutant factor. The number tells you how long the sun’s UVB rays would take to redden your skin if you apply the sunscreen compared with no sunscreen use. So, if you use an SPF 30 product properly, it would take you 30 times longer to burn than if you used no sunscreen. (5)
Figure 3. SPF selection guide (6)
Are sunscreens safe?
Although physical sunscreens may be less likely to cause skin irritation than chemical sunscreens, both types have always been tested as safe and effective. In fact, many sun protection products available today combine both types of ingredients.
Here are some useful tips for a better use of sunscreens:
1- Look for Broad spectrum that protects your skin from both UVA and UVB rays.
2- Use SPF 30 or higher for extended outdoor activities.
3- Choose water resistant or very water resistant when swimming, because all sunscreens aren’t water proof, but these two kinds are tested to be effective for up to 40 minutes, and 80 minutes respectively.
4- Apply the sunscreen using “the teaspoon and shot glass rule”: 1 teaspoon of sunscreen to the face and neck, and enough to fit a shot glass (approximately 1 ounce) for exposed areas of your body.
5- It’s recommended to apply the sunscreen 15 to 30 minutes before sun exposure, then wait for 10 to 20 minutes before getting dressed. (7)
Figure 4. Tips for using sunscreens (8)
(1) https://en.wikipedia.org/wiki/Sunscreen (accessed on 30 October 2020)
(2) https://nypost.com/2019/05/26/why-switching-from-chemical-to-mineral-sunscreens-might-be-your-best-bet/ (accessed on 5 November 2020)
(3) https://www.health.harvard.edu/blog/sun-protection-appropriate-sunscreen-use-2018062114114 (accessed on 30 October 2020)
(4) Physical Sunscreen vs. Chemical Sunscreen: What’s the Difference? https://www.drmtlgy.com/blogs/drm-digest/physical-sunscreen-vs-chemical-sunscreen-what-s-the-difference (accessed on 5 November 2020)
(5) https://www.skincancer.org/skin-cancer-prevention/sun-protection/sunscreen/ (accessed on 30 October 2020)
(7) Laura Nathan-Garner, Sunscreen: Tips to wear it well. April 2017. https://www.mdanderson.org/publications/focused-on-health/Sunscreen-Tips-to-wear-it-well.h25Z1591413.html (accessed on 30 October 2020)
(8) Infographic: Your sunscreen survival guide. https://www.mysouthernhealth.com/tips-using-sunscreen/ (accessed on 5 November 2020)