Understanding Sunscreens

Ambica Gayathri Knowledge Sharing

Sunscreens are meant to protect the skin from harmful UV rays. They are usually lotions, creams, sprays or gels that protect us from sunburns, tanning and other skin diseases caused due to exposure to the sun.

In recent years, homemade or DIY sunscreens have been gaining popularity since people want more "natural" ingredients in their products or manufacture their own products. This may work in the case of lip balms or face packs, but sunscreens are not meant to be DIY or homemade because effective sunscreens are difficult to produce and need a lot of testing.

Here’s an explanation of what these harmful UV rays can do to the human skin, how sunscreens counter that and why it is best to always ask questions before buying DIY or home-based sunscreens. 

Sunscreens - An explanation by Scentora



There are two types of UV rays that can be harmful to skin – UVA and UVB. UVB rays are the ones that cause sunburns while UVA rays can cause premature skin ageing and is known to increase the harmful effects of UVB rays.

Humans require protection from both these types of rays and that is why any effective sunscreen should be broad-spectrum, that is, protect the skin from both UVA and UVB rays and they should have an SPF of at least 30. 


SPF (Sun Protection Factor) determines how long a sunscreen can protect you from UV rays when you are out in the sun wearing your sunscreen. This means that using SPF 30 sunscreens can protect you from sunburns 30 times longer than if you did not use any sunscreen at all. 

A sunscreen with SPF 30 has been known to block almost 97% of harmful UV rays and it is recommended by dermatologists to use sunscreens with SPF 30, at minimum.


A major reason why people switch to homemade sunscreens is due to the fact that commercial sunscreens are not zero-waste nor sustainable. 

Most DIY or homemade sunscreens try to replicate commercial sunscreens by heating a number of moisturizing oils and butters, and then blending them with zinc oxide. Zinc oxide is the mineral that reflects harmful UV rays and the quantities added depend on the SPF required. The SPF of the final product is then decided by adding up the SPFs of every individual ingredient.

But the problem is, these sunscreens are not properly tested and hence, it is very difficult to know how effective it can be. And risking skin and overall health on such products is also not sustainable.


Commercial sunscreens are lab-tested products that protect the skin from harmful UV rays. Such sunscreens are carefully blended since every ingredient in its specific quantity has a key function that cannot be compromised. These sunscreens are then thoroughly tested under different lab-simulated conditions to see if they can withstand harmful UV rays and are then categorized according to SPF.

Most commercially-available sunscreens have a number of organic and inorganic compounds that work to absorb and / or reflect UV rays. Inorganic compounds used are minerals like zinc oxide or titanium oxide while the organic compounds are usually avobenzone, oxybenzone and more.


Oxybenzone is a skin-safe chemical used in commercial sunscreens to absorb UV rays. Reportedly, oxybenzone in large concentrations can damage the coral reefs of the world by bleaching the corals and even disrupting the health of marine life. Avobenzone and octinoxate are also claimed to be disruptive. These claims are not scientifically proven.

What is proven to be actually damaging to the reefs is climate change and pollution. And the adverse effects of these factors rank much higher than the unproven claims about sunscreens.

It is also important to understand that these substances exist as a small component of sunscreens. And there are effective, tested and commercially-available sunscreens that do not contain oxybenzone or octinoxate too, if that is what the end user prefers.


There are many myths surrounding both conventional sunscreens and homemade sunscreens. Let's take a look at some of them to separate the myths from the facts.

Myth: The ingredients in commercial sunscreens are not safe for skin and can cause skin diseases.

Fact: These ingredients are approved, regulated and tested before commercialising the product. The quantity of ingredients used are also regulated and are strictly maintained in the formula.


Myth: Oils like coconut oil, carrot seed oil and more already have the sufficient SPF required to function as a sunscreen and therefore, that is all we need. 

Fact: Coconut oil does not absorb or block the harmful UV rays: UVA and UVB. And carrot seed oil has no verifiable SPF. Therefore, trusting such oils alone to act as sunscreens is basically the same as volunteering to get sun-damaged.


Myth: If a homemade sunscreen has enough oil and butter ingredients with SPFs that add up to the required SPF, then that sunscreen will definitely work.

Fact: SPF cannot be increased by simply adding ingredients. It is more complicated than that. A cosmetic chemist tried this experiment of making her own SPF 30 sunscreen with oils and butters that added to equal to SPF 30. She then tested that in a lab. The result showed that the homemade sunscreen was only SPF 12.


Myth: If we apply sunscreen, then we can skip the full-sleeved protective clothing and step out in the hot sun. 

Fact: Sunscreens alone are not sufficient. The best strategy to protect your skin from the sun is to use good-quality sunscreens while also shielding the skin with enough protective clothing and seeking shade whenever possible.



It is important to understand how sunscreens work before opting to buy any of them. This way you can choose the most effective one by checking for the following:

  • Is the sunscreen broad-spectrum?
  • Is the SPF 30 or higher?
  • Has this been tested for effectiveness?


This article gives an overall gist of how sunscreens work and what you should be looking for when buying them. But there's a whole lot more to sunscreens and if you would like to know more, we'd recommend you watch these well-researched YouTube videos from Michelle Wong who has a PhD in Chemistry. Her channel is Lab Muffin Beauty Science and here are her informative videos about sunscreens:

  1. Why DIY Sunscreen Doesn't Work
  2. Top 7 Sunscreen and SPF Myths
  3. How To Use Sunscreen and Make-up Together
  4. Chemical Vs Physical Sunscreens


Written by Ambica Gayathri (Co-Founder of Scentora)

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  • suvextziwk on

    Muchas gracias. ?Como puedo iniciar sesion?

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