Dermatologists recommend DAILY use of a broad-spectrum (covering a wide range of wavelengths) UVA and UVB sunscreen with a Sun Protection Factor (SPF) of at least 15, as the most effective way to protect the skin from photodamage - skin ageing caused by exposure to the sun.
Sunlight arrives on Earth in three forms; infrared (heat), visible light and ultraviolet (UV) radiation in the form of UVA (types 1&2) and UVB.
UVA light penetrates deeper into the skin than UVB light and is thought to be a prime cause of photoageing (damage to the skin caused by the sun); characterised by wrinkles, dark blotches, freckles, leathery skin and a loss of skin elasticity. 99% of the ultraviolet radiation that reaches the Earth's surface is actually UVA, yet deceptively we mostly hear about worries concerning UVB radiation, as it is this form that causes the visibly noticeable “tan” and “sunburn”. The intensity of UVA radiation is more constant than UVB without the variations during the day and throughout the year. UVA is also not filtered by glass - so make sure that you protect your skin if you drive regularly.
Sunscreens or sunblocks that partially block UV radiation are widely available and display a Sun Protection Factor, or SPF, which is a measurement of protection against the UVB rays, which cause tanning and sunburn.
A sunscreen rated as SPF15 blocks 93.3% of UVB radiation and one with SPF30 blocks 96.7%. Therefore, for example, a sunscreen with an SPF15 will protect your skin from harmful UVB light up to 15 times longer than if you wore no protection on your skin at all.
The sunscreen industry splits sunscreen ingredients into two categories, chemical and physical (mineral) filters. Chemical filters which absorb the UV rays are typically absorbed by the skin and are thought to be metabolized by the body, sometimes causing allergic reactions in some individuals; (although there is no real clinical data established for this to date). Physical or mineral filters which reflect the UV rays lie on top of the surface of the skin and are not absorbed by it or metabolised by the body.
Recent studies show that the most commonly used sunscreen ingredients protect mainly against UVB rays which cause sun burning, and not UVA rays that cause photoageing (sundamage) to the skin. In fact Zinc Oxide is the only sunscreen ingredient which blocks all three of the main types of ultraviolet radiation from the sun, UVB, UVA1 and UVA2 rays.
In addition, some newer powerful antioxidant combinations have also been proven to help protect the skin from some of the damaging effects of UV radiation.
