SPF, The Higher The Better?

The discovery of Ultraviolet (UV) radiation was associated with the observation that silver salt darken when exposed to sunlight. Ultraviolet is originated from Latin word, meaning “beyond violet”.  There are two categories of UV light which commonly harm our skin when we are exposed under the sun – Ultraviolet Type A (UVA, wavelength 320-400 nm) and Ultraviolet Type B (UVB, 280-320nm). UVB ray only have the strength to penetrate the top layer of your skin, called the epidermis, causes sun burn. While UVA ray is more dangerous, it has the strength to penetrate the second layer of your skin (dermis) which can cause skin damaging slowly, thus lead to premature aging.

Sun Protection Factor (SPF), is a measure of how well a sunscreen, suntan lotion, or similar preparation protects the skin from ultraviolet rays. It was first introduced in 1962, to measure a sunscreen effect against UVB rays. SPF is determined by choosing a number of fair skinned volunteers and the time for the skin to turn red. The product tested is then applied and the time for the skin to turn red is again measured. The different in time is the SPF. The redness in skin is caused by UV-B radiation and not UV-A radiation therefore SPF does not measure UV-A protection.

SPF number starts at 2 and have reach 130. To figure out how long you can stay in the sun with a given

SPF, you may use this equation:

      è minutes to burn without sunscreen x SPF number = maximum sun exposure time

For example, if you burn after 10 minutes of sun exposure, an SPF 15 will allow you to be in the sun for up to 150 minutes without burning. It is largely accepted that the higher the value, the greater the level of protection from sun damage to the skin, but it is not scientifically proven beyond SPF 50 are actually more effective or not.