What to look for while buying a sunscreen?

Decoding jargons like SPF, PA, UVA & UVB so you can make the right choice!


Looking to buy a sunscreen and confused by jargons like SPF, PA, UVA, UVB? Like it or not, these jargons hold the key to choosing the right product, so it is worth getting your head around it.


Let’s start at the very beginning. A sunscreen protects against the sun’s harmful ultraviolet or UV rays. If you aren’t using a sunscreen, you’re setting yourself up for conditions like skin reddening, sunburn, skin darkening, skin-aging and even skin cancer.


Stepping outdoors without a sunscreen is an absolute no-no - whether it is a sunny day or a rainy day, use sunscreen daily!


True, sunscreens don’t provide 100% protection, but they are still your first-line defence against sun damage. And the rest of the work - wearing protective clothing, using sun-glasses and avoiding the sun during the most intense hours - also need to follow.


Although sunscreen jargons sound a tad technical, they are easy to understand once you know what they are. So, let’s delve right into it.


Ultraviolet Rays - UVA vs UVB


As we all know, the sun radiates light to the earth and part of that light consists of ultraviolet or UV rays that are invisible to the naked eyes because their wavelength is shorter than visible light.


These UV wavelengths are classified as UVA, UVB and UVC. UVA is the longest at 320-400 nanometers. UVB has a shorter wavelength, but is much more intense than UVA.


UVC, the shortest wavelength and perhaps the most dangerous, gets absorbed by the earth’s protective ozone layer and fortunately does not reach us.


UVA and UVB can, however, penetrate our atmosphere and even pass through cloud and pollution. They also are hazardous to our skin - prolonged exposure can lead to skin reddening, sunburn, skin darkening, skin-aging, wrinkles & fine-lines and even skin cancer.


And it’s not just hot sunny days that you need to worry about. Since both UVA and UVB can pass through cloud, they are harmful even on overcast and cool days. Hence, the need for sun protection all year round!


UVB affects the skin’s superficial epidermis layer, causing skin reddening and sun burn. It also plays a major role in skin cancer as it can damage the skin’s cellular structure.


UVA, on the other hand, penetrates the skin deeper, affecting the dermis (which lies below the epidermis). They are also called ‘ageing rays’ as they play a key role in fine-lines, wrinkles, skin darkening and skin aging due to the breakdown of collagen.


Dr. Harini Thummuluri, Consultant Dermatologist & Cosmetologist, says 90% of UV rays contain UVA that causes skin ageing and destroys Vitamin A cells in the skin. “UVB is colloquially called ‘sunburn ray or burning ray’ because it causes DNA damage to the skin cells,” she notes.


UVA rays are present all year long, unlike UVB rays that are stronger in the summer months. In addition, UVA can penetrate through glass (unlike UVB), thus leaving you vulnerable even inside your car.


Sunscreen or Sunblock?


Most people think sunscreen and sunblock are synonymous with each other and it doesn’t matter which one they use. But the two are quite different.


As the name suggests, sunblock blocks the sun’s UV rays by creating a physical layer of protection on the skin surface. It’s usually a thickish formulation (usually a cream or lotion) that creates an opaque film on the skin so the sun’s UV rays cannot penetrate the skin, thus preventing sun damage.


A sunscreen does not block the sun’s UV rays. Instead, its chemical ingredients absorb the harmful UV rays, thus reducing the amount that reaches inside the skin. Sunscreens tend to be transparent, are invisible when applied and are easier to wash off than a sunblock.


“Sunscreen is a chemical protecting agent, while sunblock is a physical protecting agent,” says Dr. Thummuluri. Sunblocks acts as a shield - when the UV rays hit the skin, they bounce off and do not get absorbed. Sunscreen acts more like a filter, absorbing the UV rays.


Sunblocks are an excellent choice for people with sensitive skin. Because sunblocks are not absorbed by the skin, they don’t cause skin reaction or irritation. But because they leave a white cast/residue on the skin, they don’t find universal appeal.


Also, for oily and acne-prone skin, sunblock can be a challenge. This is because the pore openings of the skin may get blocked, leading to a breakout.


Speak to your dermatologist to know if sunblock suits your skin or whether you are better off with a sunscreen.


What are SPF & PA?


SPF - or sun protection factor - is a measure of a sunblock or sunscreen’s ability to prevent UVB rays from damaging the skin. SPF indicates how much time you will be able to withstand exposure before burning up or skin darkening.


In other words, if it takes 10 minutes for an unprotected skin to start turning red, using an SPF 15 sunscreen will theoretically prevent reddening 15 times longer - i.e. about 2 and-a-half hours!


A higher SPF will obviously provide better protection against UVB rays, but most experts are of the opinion that SPF-30 is good enough for darker skin, while SPF-50 is suitable for lighter skin that tends to burn more easily.


When applied correctly SPF-30 will block 96% of sunburn causing UVB rays - thereafter the higher you go, the difference is marginal. For example, SPF-50 will block 98% and SPF-75 99%. There’s no way to block 100%!


SPF only measures protection against UVB (or sunburn rays). For the best protection, you also have to protect against UVA (or aging) rays.


That’s where PA - or protection grade of UVA - helps. PA is a measure of protection efficacy towards UVA rays. PA+ means some protection, PA++ indicates moderate protection and PA+++ shows very good protective abilities. PA is an older measure, used mostly by Asian brands.


So, when buying a sunscreen, opt for one that offers broad spectrum protection - i.e. protects from both UVA (aging rays) and UVB (burning rays).


How to choose a Sunscreen?


Different skin types have different requirements, so you need to choose the right sun protection based on your skin type to get the best results. Otherwise, it may do more harm than good!


Dry skin requires a moisturizing sunscreen; experts recommend a cream-based one with lanolin, dimethicone and silicones. For normal skin, opt for a matt-finish sunscreen with an SPF of 30.


Oily skin needs a gel-based sunscreen, which is non-greasy, fragrance-free with less added preservatives. If opting for a sunblock, go for a zinc oxide based one, as it won’t clog your pores, notes Dr. Thummuluri.


And the best time to apply sunscreen is 30 minutes before venturing out into the sun. Apply the sunscreen on all the exposed areas of the skin like face, neck, hands, legs and feet. 


And remember, using a sunscreen does not guarantee day-long UV protection. The maximum effect lasts for 2-3 hours after which the protection reduces gradually. And why is that? Because sweat and heat break down the effectiveness of a sunscreen.


So, don’t forget to re-apply every 2-3 hours if you are outdoors. Re-application may not be required that frequently if you remain indoors.


- Rahul Lahkar, Saralhealth Bureau, Bangalore


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