SPF stands for sun-protection-facotr. It indicates the level of protection a sunscreen provides. SPF is measured in photon absorption. Sun exposure leads to 80% of ageing, and as we know, can cause a hurtful burn. But is a sunburn the worst the sun can offer?! No. UV radiation emitted by the sun causes structural, enzymatic and genetic damage, which can lead to cancer. Sunscreens containing SPF help to mitigate the harmful effects of UV radiation.
Cosmetic Ingredients Series
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Why is SPF Important?
Sunscreens are cosmetics which protect our skin from harmful UV light. They block the UV light from coming into contact with our skin (though not 100%), so that our skin does not burn and cause pre-mature ageing of the skin. Without it, many people wouldn’t be able to withstand prolonged exposure to the strong midday sun.
We typically bang on about the cosmetic benefits of skincare ingredients on this website, however, sunscreen product’s primary function is not to provide benefits, its to prevent damage. A good skincare routine is anchored around prevention, not treatment, which sunscreens are a major part of.
UV exposure is a major contributor in skin related cancers. It’s interesting to note that there are three main factors at play here:
- Ethnic makeup of population (melanin concentration).
- Geographical location (distance from equator).
- Ozone integrity (blockage of UVB and UVC radiation).
Depending on your genetic makeup, geographical location and if your government has banned chlorofluorocarbons will impact your sunscreen usage.
Types of UV radiation
Ultraviolet radiation can be grouped into three categories based on their wavelengths. These wavelengths determine the penetration of substances, giving them unique properties. The longer the wavelength (lower frequency), the higher the penetration.
UVA
Wavelength: 320-400nm
Due to its long wavelength, UVA radiation can penetrate through the atmosphere, passing beyond the epidermis and reaching the dermis, the deeper layer of the skin. This deep penetration leads to the degradation of collagen, a critical structural protein, ultimately causing the skin to age prematurely. In other words, prolonged exposure to UVA radiation contributes significantly to the ageing process of the skin.
Importantly, UVA radiation remains potent and harmful even on cloudy days. Unlike UVB rays, which are largely absorbed by the ozone layer, UVA rays can penetrate through the ozone, clouds, and even glass windows. This means that individuals are continuously exposed to these ageing rays, regardless of the weather or whether they are indoors or outdoors.
Given this pervasive threat, it is strongly recommended to apply sunscreen every day, choosing products that offer high UVA protection. Consistent use of sunscreen helps to shield the skin from the damaging effects of UVA radiation, preserving skin health and maintaining a more youthful appearance over time.
UVB
Wavelength: 280-320nm
This specific range of wavelengths corresponds to UVB radiation. UVB rays have a shorter wavelength compared to UVA rays, which means they primarily penetrate only into the epidermis, the outermost layer of the skin. Despite this limited penetration, UVB rays are highly energetic and can cause significant damage with excessive exposure. One of the most immediate and noticeable effects of UVB exposure is sunburn. Sun Protection Factor (SPF) in sunscreens specifically refers to the level of protection provided against UVB radiation.
UVB radiation directly links to skin burning and is a major cause of skin cancer. When UVB rays expose epidermal cells, they trigger apoptosis, or programmed cell death, as a protective measure to prevent the spread of damaged cells. However, UVB exposure can also cause genetic damage that, if not properly repaired, can lead to mutations and the potential development of cancerous cells.
It’s important to note that while UVB radiation is partially blocked by clouds, reducing the intensity of exposure, it is not completely eliminated. As a result, while sunburn is less common on cloudy days, it is still possible, especially with prolonged exposure. Therefore, even on overcast days, some level of sun protection is advisable to mitigate the risks associated with UVB radiation.
UVC
Wavelength: 100-220nm
UVC radiation has a very short wavelength, and as a result, it cannot pass through the ozone layer. Most sunscreens are not designed to protect against this form of radiation because, under normal circumstances, UVC does not reach the Earth’s surface.
The ozone layer plays a crucial role in absorbing and blocking the majority of UVC radiation from reaching the ground. However, human activities have compromised the stability of the ozone layer. In particular, the widespread use of chlorofluorocarbons (CFCs) in aerosols and other products has had a detrimental impact. CFCs are stable compounds that, once released into the atmosphere, gradually rise up to the stratosphere, where they are broken down by ultraviolet light, releasing chlorine atoms. These chlorine atoms react with ozone (O3) molecules, leading to the depletion of the ozone layer.
This depletion of the ozone layer has resulted in the formation of a significant “hole” over Antarctica, which affects nearby regions such as Australia and New Zealand. The thinning ozone layer over these areas has allowed higher levels of ultraviolet radiation, including potentially dangerous UVC radiation, to reach the Earth’s surface. Although UVC radiation is still largely absorbed by the remaining ozone, the increased UVB exposure due to ozone depletion has had severe health impacts.
Australia and New Zealand have experienced a dramatic increase in cases of melanoma and other skin cancers, attributable to the heightened levels of UV radiation exposure. The ozone layer above Australia has not yet fully recovered, maintaining elevated risks for residents in these regions. Efforts to reduce CFC emissions globally, such as the Montreal Protocol, have been successful in curbing further damage to the ozone layer.
Physical Sunscreen
These sunscreens contain ingredients that physically block UV rays. UVA and UVB radiation are reflected from the surface of the skin back into the atmosphere, preventing the radiation from penetrating the skin. These sunscreens are made up of mineral or inorganic ingredients, such as titanium dioxide and zinc oxide.
Physical sunscreens work by creating a protective barrier on the skin’s surface that reflects and scatters UV radiation. This is in contrast to chemical sunscreens, which absorb UV radiation and convert it into heat that is then released from the skin. The primary ingredients in physical sunscreens, titanium dioxide and zinc oxide, are both effective at providing broad-spectrum protection against UVA and UVB rays.
Titanium dioxide offers strong UVB and partial UVA protection, while zinc oxide provides excellent broad-spectrum protection, covering the full range of UVA and UVB radiation. Together, these ingredients create a comprehensive shield against sun damage.
In addition to their UV-blocking capabilities, dermatologists often recommend physical sunscreens for individuals with sensitive skin because they are less likely to cause irritation compared to chemical sunscreens. Physical sunscreens also maintain their effectiveness throughout the day, as they are photostable and do not degrade when exposed to sunlight.
As awareness about the environmental impact of personal care products grows, more consumers are turning to physical sunscreens as a safer choice for both their skin and the planet. While they may require more frequent reapplication and might not be as cosmetically elegant as chemical sunscreens, their benefits make them a valuable option in the ongoing effort to protect skin health and the environment.
Pros of Physical Sunscreen
- Safe for pregnancy and babies.
- Less likely to irritate the skin.
- Better for people with heat sensitivity.
- Supposedly more eco-friendly.
Cons of Physical Sunscreen
- Easily rubbed/sweated off.
- Can appear white/chalky.
- A thick layer must be applied.
Chemical Sunscreen
These sunscreens contain ingredients that absorb and dissipate UV rays. When UVA and UVB radiation hit the skin, the chemical ingredients in the sunscreen absorb the UV energy and convert it into heat. This heat is then dissipated across the skin’s surface, leading to a slight increase in temperature. This process prevents the UV radiation from penetrating deeper into the skin, thereby protecting against sunburn and other forms of UV damage.
Chemical sunscreens are the more popular form of sunscreens, primarily because they are generally more comfortable to wear and tend to last longer on the skin. They are often formulated to be lightweight and easy to apply, blending seamlessly without leaving a visible residue. This makes them more aesthetically pleasing and convenient for daily use.
However, chemical sunscreens can have some drawbacks. One of the concerns is that they can be comedogenic, meaning they have the potential to block pores. This can sometimes lead to acne, particularly in individuals with oily or acne-prone skin. Despite this, many people prefer chemical sunscreens due to their ease of use and effective sun protection.
Pros of Chemical Sunscreen
- Thinner, easier to apply.
- Skincare routine compatible.
- Smaller volume of product needed.
Cons of Chemical Sunscreen
- Can be irritating to the skin/eyes.
- Only becomes effective after 20 mins.
- Can clog pores and increase acne.
What Is SPF?
SPF stands for sun-protection-facotr. It indicates the level of protection a sunscreen provides.
We measure the SPF factor by comparing how long your bare skin can be exposed to the sun before burning to how long it takes for your skin to burn with an applied SPF.
If your skin is prone to burning after 10 minutes of direct exposure to sunlight, applying a sunscreen with and SPF of 15 would allow you to stay in the sun for (10 x 15) 150 minutes, or 2.5 hours.
SPF = mins taken to burn with SPF / mins taken to burn without SPF.
SPF 15 = 150 minutes / 10 minutes
These calculations take data from an SPF test study performed under ISO 24444. Under this standard, all testing must be performed, and each product on the EU/UK market with a stated SPF value must undergo this specific testing as a regulatory requirement. 1/3 of the stated SPF factor must be UVA protection, however, certain products can be better are shielding from UVA radiation than others.
How does SPF Protect your Skin?
Photons are unique in that they exhibit properties of both particles and waves, a duality that allows them to interact with matter in various ways. When photons from UV radiation reach the skin, they are highly energetic and can induce significant chemical changes in the skin cells they interact with. This interaction occurs because the photons possess enough energy to penetrate the cells and interact with their DNA.
When photons strike the DNA within skin cells, they can cause molecular damage. This damage can lead to mutations in the DNA, which, if not properly repaired, can accumulate over time and potentially lead to skin cancers. If the damage is extensive, the cell may initiate a process called apoptosis, or programmed cell death, to prevent the propagation of damaged DNA. This process manifests as sunburn, which is the body’s way of eliminating cells that have sustained too much damage to function normally.
Not all sunscreens protect the skin by the same amount.
A moisturiser with no SPF will let all the photons through. A moisturiser provides 0% protection.
A sunscreen with SPF 15 will let 7 photons through. Sunscreens with SPF 15 provide 93% protection.
A sunscreen with SPF 30 will let 3 photons through. Sunscreens with SPF 30 provide 97% protection.
Melanin, the natural sun protector, plays a big role in how important sun protection products will be in your life. It’s true, individuals with a high melanin content have a high tolerance to sun exposure, and rarely burn. This is why SPF testing is conducted on individuals with Fitzpartick skin types I and II.
The effects of UV exposure
Photoaging is by far the most significant contributor to skin aging. Photoaging refers to the premature aging of the skin caused by repeated exposure to ultraviolet (UV) radiation, primarily from the sun. This process involves the induction of reactive oxygen species (ROS), highly reactive molecules that can cause significant cellular damage. These ROS interact with and degrade the matrix metalloproteinase-1 (MMP-1) protein, which is crucial for collagen production in the dermis. Collagen is a structural protein that provides support and elasticity to the skin.
When UV interference degrades collagen, it causes the dermis to lose its structural integrity. This degradation weakens both the epidermis and the stratum corneum, leading to visible signs of aging like fine lines, wrinkles, and loss of firmness.
This degradation underscores the importance of incorporating sunscreen into daily skincare routines. Sunscreen is essential for protecting the skin from the harmful effects of both UVB and UVA rays. Sunscreen packaging indicates UVB rays’ responsibility for causing sunburn through the Sun Protection Factor (SPF) value. The SPF value denotes the level of protection provided against UVB radiation.
UVA rays penetrate deeper into the skin and cause photoaging, including wrinkles and fine lines. Some sunscreens disclose UVA protection, but it’s not always indicated. Therefore, choosing a broad-spectrum sunscreen that protects against both UVA and UVB rays is essential for comprehensive sun protection.
