Sun protection is essential, even if you don't spend a lot of time outdoors.
Other than painful burns, the sun is also the main cause of premature skin ageing i.e age spots, dullness, wrinkles and chronic dehydration. These signs only creep up on us many years later in our lives, where we will then spend an even longer time trying to reverse the damage.
Why is the sun so detrimental to skin health? How can it affect us even if we are not directly exposed to it?
Why is sun protection so important?
The sun emits ultraviolet (UV) light. Amongst this spectrum, the two types of radiation, UVA and UVB, are the most harmful to skin.
UVA and UVB have different wavelengths, and can thus thus penetrate skin to different extents. Simply put, UVB burns us while UVA ages us.
UVB is mostly absorbed in the epidermis. It causes redness (erythema), burning, blistering and peeling depending on the length and extent of exposure. It induces (delayed) tanning by increasing skin's melanin production due to sun exposure.
UVA penetrates deep into the dermis, capable of destroying its collagen and elastin structure. It is the primary cause of the signs of premature ageing (photo-ageing) such as fine lines, wrinkles, dryness, dehydration, sun/age spots and sagginess due to the loss of elasticity. UVA also causes of immediate skin darkening with exposure, due to the oxidation of existing melanin present in the skin.
Both UVA and UVB are capable of damaging cellular components including DNA, which can result in mutations and skin cancers. Although UVB rays are blocked by materials such as glass and clouds in the sky, UVA can pass through them easily and penetrate the skin. Thus, sun protection is important whether you are indoors or outdoors.
How do sunscreens protect us?
Sunscreens contain sun filters that protect us by limiting the sun's UV radiation from penetrating the skin.
There are two types of sun filters, physical and chemical, that prevent UV from entering the skin. Their mechanisms are different: (i) physical sun filters reflect UV rays; (ii)chemical sun filters absorb then convert UV radiation to heat.
How is sun protection measured?
UVB protection is measured using SPF (sun protection factor) values. A higher SPF gives a higher level of UVB protection, though this value is not directly proportional to the extent of protection - i.e SPF 20 protects against 95% UVB, while SPF 50 protects against 98% UVB.
UVA protection measurement, unlike UVB, is not universal. Different parts of the world use different methods to measure the level of UVA protection. Most of Australia, USA and Europe use a pass/fail system - products that pass carry a 'UVA' logo or indication. Asia and UK adopt grading systems like PA (+ to ++++) and Boots Star ratings respectively.
Broad spectrum protection means protection from both UVA and UVB, that is essential for protection against both burning and ageing effects of the sun.
Limitations of SPF/UVA indications
Although SPF/UVA measurements are useful indicators, the extent of protection we end up receiving is not actually the stated values, as it is difficult to account for the following variations. They are why we usually end up receiving a 'lower than stated' level of sun protection
- Amount used: Many of us apply less than the prescribed amount used in SPF/UVA testings
- Uniformity: Not applied evenly across all areas of exposed skin
- Inherent sun sensitivity: Fair skins with less melanin are more prone to UVB burns than dark skins
- Skin substantivity: How well the sunscreen stays on skin after application
- Type/duration of activity carried out after: Sweating (with swimming/running etc) allows sunscreen to come off easily
Sun protection is not only a true anti-ageing measure, but is also imperative for skin health. Since sunscreen should be a daily essential, where do we start in deciding which to use? That's coming up next, so don't go anywhere!