In our previous article, you have learnt the various categories of ultraviolet rays. To recap, UVA refers to UV rays of the 315-400nm wavelength; and UVB refers to UV rays of the 280-315nm wavelength.
In the market, the effectiveness of sunscreens is often touted with reference to ‘SPF’. Various numbers are quoted with it, ranging from 8 to as high as 50. So what exactly is SPF?
Sun Protection Factor (SPF), by definition refers to the ratio of the energy required to produce a minimal erythema dose on protected skin versus the energy required to produce such a dose on unprotected skin. To put it simply, it refers to the time required to produce minimal sunburn on your skin with sunscreen applied versus the time required to produce minimal sunburn without the sunscreen.
For example, if it takes you ten minutes in the sun to get sunburn, a SPF-15 sunscreen will last you two and a half hours before sunburn sets in (15x10 = 150 mins). Similarly, a SPF-30 sunscreen will last you 5 hours (30x10 = 300 mins), and so forth.
Be advised that sunscreens function as a ‘filter’, i.e. some UV rays still reach the skin even with sunscreen applied.
Hence, the term ‘sunblock’ is misleading and is rarely used today. A SPF-15 offers protection of up to 93.3% (14/15 = 93.3%); a SPF-30 offers protection of up to 96.6%. Looking at this, a higher SPF does not mean significantly greater UV protection; it only means you can stay in the sun longer.
Also note: SPF is measured with reference to UVB protection
only. Till date, there is no fixed standard of measurement for UVA protection. The Australian standard requires sunscreens to be able to absorb at least 90% of UVA rays before a ‘UVA protection’ claim can be used. In the industry, some sunscreens products are labeled the term “PA” followed by the number of pluses (+) following - one plus for low UVA protection and three pluses for high UVA protection. However, this benchmarking remains to be reviewed.
Some sunscreens are marketed as being “water-resistant”. Regulations stipulate that these sunscreens must be able to provide adequate sun protection after immersion in water for a fixed period of time. Notwithstanding, it would still be wise to reapply sunscreen after an extensive period in water.
Some sunscreens are marketed as being “broad spectrum”, i.e. offering coverage for both UVA / UVB protection. An international standard for this claim remains to be recognized.
In our next article, we shall share with you some pearls of wisdom concerning personal UV protection, and also visit a medical condition known as “melanoma”.
Sun Maven Tip for the Consumer:In the market, it is not uncommon to find beauty products (moisturizers, foundations etc) offering some form of UV protection. Take note that such protection is often secondary. For serious sun addicts and beach lovers, it is still wise to use a proper sunscreen for optimum protection. And if you insist on looking pretty before you hit the sand, apply sunscreen first. Allow it to sink in before applying a tinted moisturizer or very sheer foundation on top.