SPF, PA and More: sunscreens explained in simple terms
Picking a sunscreen just got a whole lot easier with this really short blog post. Here’s how…
What makes a great sunscreen? While picking a sunscreen, you need to know some basic terms that describe how strong its protection is. Here are some of these basic terms:
UV Radiation: A particular type of radiation (mostly from the sun) that causes damage to human skin including sunburn and premature ageing. Sunscreens are a must to prevent damage to the skin caused by these rays while going out into the sun.
UVA: Long-wavelength UV rays that can penetrate deep into human skin and cause long-term damage such as premature ageing (wrinkling and drying up) of the skin.
UVB: Short-wavelength UV rays that only affect the surface of the skin. They cause immediate damage such as tanning and sunburn.
SPF: Stands for "sun protection factor". The higher the SPF, the greater is the protection from UVB rays and hence from tanning and sunburn. But the amount of UV protection offered is not in direct proportion - i.e., SPF 50 is not twice as strong as SPF 25. To be practical, one should look at the SPF range rather than the absolute SPF value. E.g. SPF values in the range of 30 and above offer higher protection than SPF values in the 15-25 range. But there is not much difference in UVB protection offered by, say SPF 50 and something above SPF 50.
PA: The higher the PA value of a sunscreen, the greater the protection it offers against UVA rays and hence from premature ageing A higher number of '+' signs in a PA value means a higher PA value and higher protection against UVA rays. E.g. PA+++ offers much greater UVA protection than PA+. PA value is measured differently in some countries and is known as PPD ("persistent pigment darkening").
There are various other parameters like critical wavelength and UVA rating, but they are all some versions of SPF and PA values. In summary, make sure your sunscreen has SPF and PA (or PPD). Pick an SPF range that is suitable for your needs, e.g. low SPF (20 to 30) if you stay indoors for most of the time and higher SPF if you stay out in the sun for very long . Hope that makes things simpler! See you soon!
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