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Thinking of Making Your Own Sunscreen? Don’t.

Article Summary

  • Sunscreen formulation is hard
  • The problem with homemade sunscreen
  • No, oils won’t protect you either

A tube of sunscreen can be used up quickly when you’re applying it correctly. A shot glass for the entire body reapplied every 2-3 hours you’re exposed means even the most affordable options need to be purchased often. So when you’re scrolling TikTok and see someone mixing together their own homemade sunscreen, it’s easy to see the appeal.

Making Sunscreen is Hard - even for cosmetic chemists.

In the U.S., sunscreen is considered a drug. This means any sunscreen being sold must meet strict requirements, like independent testing to determine the SPF rating and broad spectrum. Water resistance claims require testing as well. Stability testing is also important to ensure that the product will continue to remain effective once you bring it home and start using it.

But it’s not just a matter of whipping something up in a lab and sending it off. It can take months for even experienced cosmetic chemists to develop a sunscreen they’re happy with. You may have noticed that even the most massive cosmetics companies out there struggle to formulate sunscreens that offer both cosmetic elegance and a high level of protection - despite decades of research and development.

Here are just a few things that can influence the protection of a sunscreen:

  • the emulsifier 
  • the solvent
  • dispersal of the UV filters
  • any antioxidants in the formula

Because the new UV filters we see internationally haven’t been approved in the U.S., chemists have to work with what we have available and it can be difficult to balance an enjoyable consumer experience with protection against the full UV spectrum, keeping the sunscreen stable, and also dispersing those filters evenly in a vehicle that will deliver them in a continuous film on the skin surface - and not penetrate the skin or be rubbed away.

Many early attempts fail testing even. And this is with the expertise of cosmetic chemists and access to the best cosmetic ingredients and equipment. Amanda Foxon-Hill has been a cosmetic chemist for over 25 years and has detailed her attempts to formulate a zinc oxide based sunscreen on her blog.

The Problem with DIY Sunscreens.

We’ve talked about how even those whose job it is to formulate cosmetics can struggle with sunscreen development and why it’s so difficult. But let’s talk more about why homemade sunscreens aren’t a viable option for sun protection.

Zinc oxide clumps. This is the main ingredient you’ll see in homemade recipes since it’s broad spectrum and easy to buy. But since zinc oxide isn’t soluble in water or oil, formulators use special equipment to create suspensions where the zinc oxide is evenly distributed. If you looked at a homemade product under a microscope, you would see the holes in your protection due to clumping.

Testing is expensive. With so many factors influencing the final protection of a product, you have no way to know if a sunscreen works until you test it. Because SPF testing is done on human subjects, it can cost thousands.

Stability is everything. Even if you beat all the odds and came up with something that works, it wouldn’t work for long. Sunscreens have to be able to stay stable both in the packaging and once applied to your skin. 

It’s all about the film. Something to note is that UV filters can’t protect our skin if they’re not formulated in a product that can deliver them in a continuous film across the skin surface and keep them there. If you’ll be swimming or sweating, further testing  is needed to confirm water resistance.

No, Oils Don’t Work Either.

Homemade sunscreen recipes pop up every summer and with it, the myth that you can get protection from raspberry seed oil or other plant oils. The only DIY that can offer any meaningful protection are hats and other clothing that are light blocking - paired with sun avoidance.

Myth: red raspberry oil is SPF 30+.

This myth seems to trace its origins to an old study that found raspberry oil to work well at absorbing UV-B light. However, the study design appears to have been flawed and newer studies3 that tested it on human skin determined the SPF was only 2.6.

SPF ratings are based upon testing on human skin and the product is applied at 2 mg per cm2. So with actual usage of an oil, the SPF rating is likely even lower than 2.6 since it would be difficult to apply that much and the oil isn’t formulated to remain on the skin.

Testing of other popular oils like coconut, carrot, and rosehip seed oil yielded similarly disappointing results.

So don’t risk your health this summer. Sunscreen isn’t just a skincare product being used for purely cosmetic purposes, it’s your protection against UV radiation. There are many sunscreen options out there that can work for your budget and have been tested.

References 

  1. https://www.fda.gov/drugs/cder-conversations/update-sunscreen-requirements-deemed-final-order-and-proposed-order
  2. https://realizebeauty.wordpress.com/2012/12/30/the-trouble-with-making-your-own-sunscreen/
  3. https://pubmed.ncbi.nlm.nih.gov/33721242/
  4. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9414157/


Mira is a skincare educator, blogger, and the content creator behind Skin Science by Mira and The Skincare Forum on Facebook. While skincare keeps her busy, she’s also pursuing her degree in Nursing and loves to spend her free time hiking.  As a content writer for Stratia Skin, Mira shares her evidence-based approach to skincare topics and a passion for making science accessible.  

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