Understand the science behind sunscreen

Introduction

Selecting a suitable sunscreen from all commercially available sunscreens becomes a tedious task because lot of companies claiming better sun protection and a variety of sunscreens available with different SPF’s ranging from SPF 15 to SPF 70 or 90. So to decide what sunscreen to buy we should understand how a sunscreen works, what is SPF and how can sun damage our skin?

How does sun damage our skin?

To start with first of all let’s understand how can sun rays damage our skin? Sun rays that enter the atmosphere of the earth consist of three components- infrared rays causing heating effects, visible light and ultra violet radiations.

The matter of concern is ultraviolet radiations as they have the most deleterious effects on the skin. UV rays are of two types- UV-A and UV-B. The UV-A rays or the longer wavelength UV rays are more harmful as they penetrate the skin deeper and are responsible for skin cancer and other changes like hyperpigmentation and photoaging. The UV-B or shorter wavelength UV rays are the rays that cause reddening of skin. The reddening of the skin occurs if exposure is greater than twenty minutes.

Sunscreen contains SPF that helps us protecting from the radiations. SPF as we commonly say is SUN PROTECTION FACTOR or in simpler words amount of sun damage that can be prevented using a sunscreen. SPF 15 is the minimum SPF that should be used. SPF 15 blocks 93% UV rays, SPF 30 blocks 97% and SPF 70 blocks 98% UV rays. Regardless of what SPF you have applied all sunscreens are ineffective after 2 hours, so you need to reapply sunscreen after every two hours and it is also noteworthy that sunscreen should be applied at least twenty minutes before going out in sun so as to have maximum benefits.

Buyer’s guide

  • The minimum SPF should be 15 and most of the moisturisers and aftershaves already have SPF 15 so you need not apply sunscreen again.
  • When you have to buy a sunscreen go for broad spectrum sunscreen which blocks both UV-A and UV-B rays.
  • Sunscreens that have benzophenones, avobenzone, titanium dioxide, zinc-oxide, oxybenzone are most protective against UV-A rays.
  • Sunscreens that have PABA derivatives, salicylates, octyl methoxy cinnamate and cinoxate are most effective against UV-B rays.
  • If you have to swim or your work is where you sweat a lot go for water resistant or extra water resistant sunscreen.
  • Any and every sunscreen requires reapplication every 2 hours.
  • If you have oily skin go for gel based sunscreens and if you have dry skin you can go for cream based sunscreens.

Sun protection tips

  • It is best avoid direct contact with sunlight between 10a.m to 4p.m as sun rays are maximum during this time.
  • Do not forget to apply sunscreen even on a cloudy day as about 40% UV rays reach earth on a cloudy day and we tend to spend more time outdoors on such a day.
  • Cover yourself with caps, hats, scarves and a good quality UV blocking sunglasses.
  • Although tanned skin is a fashion statement but avoidance is better as too much sun basking can cause sunburns and skin cancer.
  • If you have to be in sun for a long time, apply a liberal amount of sunscreen after every 2 hours or immediately after a water sport or lot of sweating.
  • Always try and use a broad spectrum sunscreen of SPF 15 or more as a daily skin care regime.
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Dr. Sanjeev Gupta

MD, DNB (Dermatology, Venereology and Leprology) | Professor and Head of the Department (M.M. Institute of Medical Sciences and Research)

Mullana Medical College, Ambala

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