How does sunscreen even work?

Why beauty influencers tell you to use sunscreen on your face?

Ever wondered what goes on “behind the screen” that protects your face from the sun? I have the answer for you, and you’re going to love it.

First, you’ll need to understand what UV rays are.

UV rays stands for UltraViolet rays. Physicists describe a spectrum of rays, all classified according to different wavelengths and frequencies. These rays exist all around us. X-rays, microwaves, and UV-rays are all included in this list.

UV-rays are further divided into three bands according to their wavelength: UV A, UV B, and UV C. The rays naturally come from the sun, and as they pass through the Atmosphere surrounding the Earth, 90% of UV B and all of UV C gets blocked. So, the rays that hit our skin on Earth are mostly UV A, and some amounts of UV B. 

This is one of the reasons why the depletion of the Ozone layer is a big problem, and why Sunscreen is such a necessity!

What each type of UV can do to our skin


These rays cause aging and skin pigmentation. They go deep into the layers of our skin and can damage the DNA of our skin cells. They also stimulate inflammation, redness, and sore-ness.


This is the ray type mainly responsible for sunburns. These rays cause a particular type of DNA damage that leads to a type of cancer called Non-melanoma Skin Cancers.

Now that we understand What UV rays can do to us, let’s take a look at how we can protect ourselves.


The most useful and effective way to protect yourself is to use Sunscreen. Scientist call sunscreens as the Primary Protective Factor.

The sunscreens which we use on our skin have something called an aromatic compound conjugated with a carbonyl group. This allows High Energy UV rays to be absorbed by the sunscreen safely. It then emits a safer version of the rays away from our body.

However, not all sunscreens can protect you from both UV A and UV B. They have to have some specific chemical compounds with a particular molecular structure to be able to do so.

That’s why it’s important for you to check that before you buy!

What is SPF?

SPF stands for Sun Protection Factor. It’s a measure of the strength of the sunscreen you are using.

Let’s say you have a person’s arm that is not protected by sunscreen. Now the amount of UV rays needed to cause a sunburn on that skin is measured. Then, on the other arm, sunscreen is applied. The amount of UV rays needed to produce a sunburn on this protected skin relative to the unprotected skin is the SPF of the sunscreen. How much more UV rays are needed to produce a sunburn when the skin is protected by sunscreen?

You might need a minimum of SPF 15 for adequate protection. The fairer the skin, the higher is the SPF requirement. So, speak to your dermatologist to choose the right SPF for you! However, as a general rule, higher SPFs are always better than lower ones.

How should you apply the sunscreen?

In order for the sunscreen to work, it needs to be applied correctly. After all, it is a screen. To work, it needs to be applied in the right amounts and the right places.

Use a liberal amount on your skin and spread it evenly. Scientifically, it is measured as 2mg every cm 2 body surface area. That’s why adding dots on your face and spreading it evenly works!

Make sure you reapply it every 2 hours, and after sweating or swimming.

Now, it’s important to know that some of the chemicals in the sunscreen can cause skin irritations and allergies. A patch test is always recommended before you try a new product!

My recommendation

A sunscreen product I personally use and would recommend is the Skinvest’s Sunny Side Up Sunscreen. It contains Zinc Oxide which offers protection against both UV A and B rays. It also has some antibacterial properties!

The product has an additional trick up its sleeve. It not only prevents skin damage, but also repairs the damage. It contains antioxidants and some Botanical extracts which allow it to do so.

I’ve used it myself and I’m really happy with the product. I have acne prone skin, so its non-comedogenic properties are perfect for me. It is also non-sticky, non-greasy, and very lightweight.


Written by-

Dr. Samira Davalbhakta
Doctor and a medical blogger + content creator

She has worked to break down health related concepts to simple bites for the masses to understand
Her blog:
Instagram: @medwithsam
She also conducts webinars and counselling sessions for medical students who want to practice in the UK.
Email for more information


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