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"Ask A Scientist About": UVA & UVB Light

by Lena Shaw, on Apr 16, 2018 11:01:29 AM

Welcome back to “Ask A Scientist About”, a series created on the belief that the more you know about science, the more you can prepare for a healthier future. Each of the articles in the series will dive into complex and often confusing topics that have become increasingly important to modern health, such as how to maintain mental sharpness, what exactly is “gut health”, and how the environment affects the aging of our skin. Our goal is to highlight several key areas that are actionable and relevant to making informed decisions about your health.

We previously covered bacteria, illustrating just how these single-celled organisms can have a symbiotic or parasitic relationship with humans - adapting and thriving in various different environments. Our second article in this series is focused on UVA and UVB light and how these UV rays from the sun relate to the health of your skin - our largest, most resilient organ.

Some of you may already know that sunlight is important for helping us to produce Vitamin D, but these rays can also be harmful, speeding up skin cell mutation - causing wrinkles, discoloration and in some cases, cancer.  In order to properly protect our skin, it’s important to learn more about how our skin processes these rays and how they cause damage and mutations to our cells.


Our very own Silene Biotech scientist, Cameron Rementer, was the perfect person to talk about UVA and UVB.  Cameron received his PhD from the Department of Bioengineering at the University of Washington, is the Science & Regulatory Lead at Silene Biotech and is a skincare addict.

Cameron, thank you for helping us learn a little bit more about UVA and UVB rays. Now, let’s get educated!

SILENE BIOTECH: What is ultraviolet light?

CAMERON: Ultraviolet (UV) light is a form of radiation from the sun. It is similar to the visible light that we see but has a shorter wavelength, which means it has a higher energy than visible light. Even though we cannot see it, we can see its effects when we spend too much time in the sun and get burned.

UV light can be further divided into UVA and UVB light. UVB light is lower wavelength (higher energy) than UVA light.

SILENE BIOTECH: Can you explain what does ‘higher energy’ mean?

CAMERON: Light is made up of photons which carry the light energy through space. Higher energy light photons vibrate faster than lower energy light photons. When these particles hit our bodies, they can knock atoms around, like your DNA.

SILENE BIOTECH: Can you explain the relationship between Vitamin D and UVA/UVB rays?

CAMERON: Vitamin D is an important vitamin that helps our bodies to absorb calcium. Without enough of it, a number of health problems can occur, including weakened bones. Vitamin D can be obtained from food, but can also be produced in the skin when UV light reacts with the precursor* to vitamin D. This reaction occurs very quickly and some groups such as the American Association of Dermatologists believe there is no safe level of sun exposure due to the negative effects of UV radiation [1].

*Additional Info: the skin contains a precursor molecule, or the “starting supplies” to Vitamin D: 7-dehydrocholesterol. Under exposure to ultraviolet rays, the precursor is converted into cholecalciferol, also known as Vitamin D3.  

SILENE BIOTECH: Can you explain the health benefits and negative effects of any exposure to UVA/UVB rays?

CAMERON: Production of Vitamin D through UVB exposure is probably the most important health benefit in humans as explained above. However, there are a number of negative effects caused by long-term exposure to UV rays.

UVB rays cause direct damage to DNA by causing changes in the DNA structure. This can result in sunburn, as well as skin cancer and other diseases. Another problem that UV light causes is damage to the proteins that make our skin strong yet stretchy. UVA causes less direct DNA damage, but is more common and penetrates the skin more deeply. This can lead to “photoaging” in the form of fine lines, wrinkles, discoloration, and other changes to the appearance of the skin.

SILENE BIOTECH: What ingredients are the most beneficial when looking for a sunscreen? What are the most harmful?

CAMERON: There are two broad categories of sunscreen: chemical and physical (aka mineral). Chemical sunscreens work by absorbing UV rays and releasing them as heat. They include many different compounds, but some common ones include oxybenzone, avobenzone, octisalate, octocrylene, homosalate and octinoxate. They provide good coverage and are available in water-resistant formulations. However, exposure to UV light causes them to break down over time (as part of their sun protecting effect), so it is necessary to re-apply. Also, some people with sensitive skin might find chemical sunscreens can cause irritation.

Physical sunscreens, also known as mineral sunscreens, are made from mineral pigments suspended in lotion. Common physical sunscreen ingredients include titanium dioxide and zinc oxide. They work by reflecting/scattering UV light which means they don’t break down over time. However, they can rub/wash off more easily so they still need regular reapplication. Additionally, some physical sunscreens are more likely to give the skin a “white-cast” due to the color of these pigments.

Some people have expressed concerns about the long-term health effects of some of the chemical sunscreen ingredients, but more research is needed. If you have sensitive skin, physical sunscreens might be a better option. Certain ingredients can actually increase the risk of burning, including Vitamin A derivatives and citrus-based products, so these ingredients should be avoided.

SILENE BIOTECH: What are some interesting scientific research or studies that we should take note of?

CAMERON: Some interesting research has been done on the effects of the food we eat on sun protection. Many plants contain specific compounds, such as polyphenols, that may be able to protect against the harmful effects of the sun. Polyphenols can be found in tea, cocoa, coffee, as well as many other fruits and vegetables. Some early research has found that these compounds can lessen the damage caused by UV rays in humans [2]. However, this is not a substitute for consistent sunscreen use.

SILENE BIOTECH: Anything else we should know?

CAMERON: When picking a sunscreen, look for the words like “Broad Spectrum” because this means it provides protection against both UVA and UVB. SPF, which stands for sun protection factor, gets a lot more attention but SPF only measures protection from UVB rays. Additionally, some countries do not allow sunscreens to be marketed as higher than SPF 50 as this might give people a false sense of security in the sun. All sunscreens need to be reapplied every 2 hours or after swimming/sweating.

Also, try and find something you like to use. One of the most important aspects of proper sunscreen use is consistency. You won’t use something if you don’t like the smell or consistency. There’s a ton of different brands and formulations so look for samples/trial size containers and keep looking until you find a product you will use every day.

SILENE BIOTECH: Cameron, thank you for educating us!


In conclusion, whether you’re someone who lives in Florida or Seattle, the sun affects us all.  Our skin absorbs these rays and converts it into healthy Vitamin D. Unfortunately, for all of those sunbathers out there, too much sun exposure and the incorrect or insufficient sunscreen could lead to wrinkles, sunburns, and in some cases, cause diseases like skin cancers.  We should all be conscious of the ingredients in products and how they relate to our skin to make sure we are well protected and we stay healthy. A helpful reminder for people who are advocates of their own health. Stay tuned for our next article in this series!


[2] Saric S, Sivamani RK. Polyphenols and Sunburn. Int J Mol Sci. 2016 Sep 9;17(9). pii: E1521.



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