|
The sun gives energy in the form of light waves
of different lengths and intensity. The sunlight
we see is called visible light. Ultraviolet
radiation (UVR) is located just above visible
light. UVR is divided into different energy
levels from shortest to longest wavelengths: UVC,
UVB and UVA.
UVC: The UVC rays have the
shortest wavelength, the most energy and
fortunately do not penetrate the atmosphere.
UVB: The UVB rays are the most potent
rays that reach the earth. UVB rays cause
sunburn (think B=Burning) and can also lead to
the development of skin cancers. SPF (Sun
Protection Factor) ratings measure a product's
ability to block UVB rays.
UVA: The UVA rays, while having less energy,
penetrate deepest into the skin. These rays
cause ageing (Think A=Ageing). It is the least
associated with skin cancer, but if delivered in
high dosages can cause skin cancer, allergic
reactions, darkening and pigmentation of the
skin (age spots, freckles), and acceleration of
the ageing process. After chronic, long-term
exposure, the skin may appear dry, scaly,
spotted, wrinkled and leathery.
As a dermatologist, I recommend daily use of
a broad-spectrum (UVA/UVB) SPF 15+ or higher
sunscreen for optimal sun protection. There is
often confusion around SPF ratings. For example,
SPF 20 means that you can stay in the sun 20
times longer than without sunscreen before
starting to burn. A product with SPF 5 covers
80% of sun rays; SPF 10 covers 90%; SPF 20
covers 95%; and SPF 30 covers 97%. Whatever the
SPF value, wearing sunscreen should not give you
a false sense of security.
SPF measurements don't strongly factor in all
the damageing UVA rays. So it's important to use
a broad spectrum product formulated to also help
block most UVA rays as well. Plus, the
cumulative effect over a lifetime of the UVB &
UVA rays that still get through when wearing
sunscreen is not negligible. Application as
frequently as needed is important (e.g., at
least every two hours when sweating or
swimming). Also, protective clothing and shelter
during midday, at high altitudes, and from
reflective surfaces can protect your skin from
skin cancer and premature ageing.
|
