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.