Daily sunscreen application is one of the best things you can do for your skin. Not only does regular sunscreen use protect us from sunburn and most skin cancers, but it can also delay skin aging!
This is because chronic UV exposure is the leading cause of premature skin aging. But what about the dangers of visible light for skin?
Prematurely aged skin is different to naturally aged skin as it occurs earlier in life and presents differently .
Premature Aging Vs Natural Aging
As you naturally age, you lose some of the fat padding in your face which results in fine lines and thinning skin. Naturally aged skin is usually smooth and unblemished and rarely occurs before your 40s.
In contrast to this, premature aging due to sun exposure (photoaging) causes the breakdown of collagen and elastin in the skin which leads to deeper wrinkles, brown marks (hyperpigmentation), and dry and leathery skin .
In fact, in one study, daily application of a broad-spectrum sunscreen over a four-year period led to younger looking skin. Even more impressively, skin appeared to have not aged at all in that four-year period of daily sunscreen use .
Most of us know the importance of protecting our skin from UV radiation. However, what about other forms of solar radiation?
Solar radiation that reaches the surface of the earth is composed mainly of infrared radiation (780-5000nm), visible light (400-780nm), and UV radiation (290-400nm) . In fact, infrared radiation accounts for about 53% of solar radiation, visible light accounts for about 39-44%, and UV radiation accounts for about 3-7%.
UV radiation is further broken down into UVA, UVB, & UVC. UVC radiation has a wavelength of 200-290nm and is unable to penetrate the earth’s atmosphere so we rarely have to worry about that one.
UVB rays are longer with a wavelength of 290-320nm and can penetrate the epidermis where they can cause obvious damage such as sunburn.
UVA rays are further divided into UVA1 (340-400nm) and UVA2 (320-340nm). UVA rays are responsible for 95% of UV radiation and can penetrate the deeper dermis where they can cause damage to cells and DNA. Furthermore, unlike UVB rays, UVA rays can penetrate glass .
Broad-spectrum sunscreens protect the skin from UVA & UVB radiation, but what about infrared radiation and visible light?
Iron oxide is not an approved sunscreen, but it is often added to mineral sunscreens to reduce white cast (iron oxide provides a reddish hue and natural tint). The addition of iron oxide to sunscreens also broadens the UV protection of mineral sunscreen agents into the UVA and visible spectrum. Iron oxide is particularly good in combination with zinc oxide and can reduce the amount of UVA rays able to penetrate the skin to 1.5% .
Visible light consists of the wavelengths of light that can be seen by the human eye and represents about 39-44% of solar radiation . It enters the skin in the same was that UV radiation does, via absorption and scattering.
When absorbed into the skin, the energy of a light photon is absorbed by what are known as chromophores (light-absorbing molecules). The depth that UV radiation is able to penetrate is dependent on the position and absorption spectrum of the chromophores in the skin.
Basically, different types of chromophores selectively absorb different wavelengths of light.
In addition, the scattering of light in the skin is dependent on the wavelength of the light – with longer wavelengths of light able to penetrate deeper into the skin . Chromophores that absorb visible light include beta-carotene, water, riboflavin, melanin, haemoglobin, and bilirubin .
The Dangers Of Visible Light
Visible Light can also lead to the production of DNA-damaging free radicals. In one study, visible light accounted for 33% of the free radical production in the substratum corneum. This was much less than the amount of free radical production from UV radiation (67%) but still demonstrates that visible light can have damaging effects on human skin .
How Can You Protect Your Skin Against The Dangers Of Visible Light?
At present, very few sunscreens provide protection against the dangers of visible light, with the exception of sunscreens that contain pigments that can absorb or reflect visible light, and sunscreens that contain a sufficient amount of antioxidants. Iron oxide is a common ingredient in foundations that can provide protection against visible light, particularly blue light.
In addition, the mineral sunscreen ingredients zinc oxide and titanium dioxide can provide some protection against the dangers of visible light .
In one study, a broad-spectrum sunscreen with added antioxidants was compared to the same sunscreen without the addition of antioxidants, as well as to the antioxidants alone before exposing skin to visible light. Exposure to visible light resulted in a significant increase in reactive oxygen species (a type of free radical).
Pre-treatment with a broad-spectrum sunscreen alone had no effect on reducing the damage from visible light. However, the addition of antioxidants into the sunscreen resulted in a significant 78% reduction in reactive oxygen species. In addition, antioxidants alone, without sunscreen, resulted in a similar reduction in reactive oxygen species, although the exact statistics were not discussed .
Related Reading: The Best Mineral Sunscreens With Antioxidants.
In terms of iron oxides protection against visible light, the majority of the research has focussed on its ability to reduce visible-light-induced pigmentation. One condition characterized by hyperpigmentation on sun-exposed areas is melasma.
In one study, patients with melasma on a hydroquinone treatment regime were instructed to use a sunscreen every day for 8 weeks, re-applying every 2-3hrs between the hours of 8 am and 5 pm. They were randomly assigned one of two sunscreens – a standard broad-spectrum SPF50 sunscreen or a similar sunscreen that also contained iron oxide. All patients experienced reductions in hyperpigmentation as is expected with hydroquinone therapy and sun protection. However, the patients who used a sunscreen with the addition of iron oxide experienced significantly greater improvements .
One downside of this study is that iron oxide wasn’t the only different ingredient in the sunscreen. Different active sunscreen ingredients were present also. This means that it is hard to be 100% sure that the effects were due to iron oxide. However, the addition of iron oxide blocked the segments of visible light adjacent to UV radiation but did not optimally filter the longer segments.
Basically, iron oxide is very effective at blocking longer UVA rays and visible light in the blue range, but its effects are less optimal as the wavelength increases.
Blue light is a high energy light close to the UV spectrum but in the visible spectrum of light. Also referred to as high energy visible (HEV) light, due to the fact that blue light photons have higher energy than other wavelengths in the visible light spectrum, excessive blue light exposure can lead to cell abnormalities and cell death . HEV light is also present in computer screens and mobile phone screens, so we are exposed much more frequently than we think.
Other research has suggested that iron oxide protection goes beyond just blue light and longer UVA radiation and is effective at absorbing all wavelengths of visible light. In fact, it significantly increases the overall photo-protection .
The same research also demonstrated that zinc oxide and titanium dioxide are far better at protecting the skin against visible light than conventional chemical sunscreen ingredients. This is because of their light-scattering properties which lead to the reflection of light off of the skin.
However, increasing the thickness of these sunscreens (and thus increasing their ability to reflect light from the skin) does not increase their photo-protective effects. The addition of an absorbing pigment such as iron oxide does, however, significantly increase photo-protection .
Related Reading: The Best Mineral Sunscreens With Iron Oxide.
Summary: How Can You Protect Your Skin From The Dangers Of Visible Light?
In order to protect your skin from the dangers of visible light and HEV light look for sunscreens with added antioxidants and iron oxide. In addition, practice other sun protection measures, such as wearing protective clothing, hats, and sunglasses (HEV light can be particularly damaging to eyes).
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