Back in 2012 I published a short post on DIY sunscreen, the gist of which was “don’t make it, you can’t know if it works.” That post continues to get a lot of traffic and quite a few comments, many of which aim to convince me that DIY sunscreen is (or can be) a good idea. So, with warmer days on the horizon (in the Northern Hemisphere, at least), I wanted to write a more detailed post on the topic. Today I’m tackling the arguments I hear from internet people who want to make their own sunscreen, using scientific articles and the help of a professional cosmetic chemist.

Why Homemade Sunscreen is Never a Good Idea

Jane Barber is the brains behind Making Skincare, and is a full member of the Society of Cosmetic Scientists. She has over 10 years experience formulating for major commercial brands such as The Body Shop, Blistex, H&M, and Boots. Her online discussion group has over 13,000 members and is packed with incredible resources and discussions. All of this is to say she has forgotten more about skin care chemistry than I will ever know! She truly knows and understands what goes into developing a reliable sunscreen formula, and why it is not a thing that should be done at home.

Before we dive in, I want to chat about what sunscreen is. It’s a substance (a spray, gel, or cream, usually) applied to protect the skin from UVA and UVB rays. The protection comes from reflecting, absorbing, and/or scattering the rays so they don’t reach our skin cells. Different active ingredients work in different ways, but in the end, any professionally developed, tried and tested sunscreen will do the same thing—protect your skin cells from harmful radiation.

Sunscreens come in a variety of strengths, labelled as “SPF”: Sun Protection Factor. SPF “is a measure of a sunscreen’s ability to prevent UVB from damaging the skin. Here’s how it works: If it takes 20 minutes for your unprotected skin to start turning red, using an SPF 15 sunscreen theoretically prevents reddening 15 times longer — about five hours. Another way to look at it is in terms of percentages: SPF 15 filters out approximately 93 percent of all incoming UVB rays. SPF 30 keeps out 97 percent and SPF 50 keeps out 98 percent.” [source]

There’s no shortage of online recipes telling you that if you mash together raspberry seed oil or coconut oil with some zinc oxide you will have magically made yourself a brilliant, all-natural, totally effective SPF 1000 sunscreen. Those people are wrong. Let’s break that down:

Argument #1: Wearing sunscreen makes you more likely to develop cancer

The argument

Back in 2000, a Swedish study on sunscreen use was released. They’d tracked 1484 people from 1995 to 1997 to monitor the occurrence of melanoma between people who wore sunscreen often, and people who didn’t. The findings were surprising; the group who wore sunscreen was more likely to develop malignant melanoma. This finding has led untold numbers of people to believe that wearing sunscreen causes cancer.

The reality

There are two extremely important details of that study that are rarely reported on: the first is that the median SPF used was 6. SIX! That is so woefully weak it’s laughable. That level of SPF is about what you’ll find on a tanning oil with an SPF; it is not meaningful sun protection. If that sunscreen was a helmet, it would be a knit toque.

The second detail is that the people who wore sunscreen reported spending much more time out in the sun, while those who weren’t wearing sunscreen avoided sun exposure. “The [odds of developing malignant melanoma were] higher in subjects who reported that sunscreen use enabled them to spend more time sunbathing.” The actual finding of the study was that wearing sunscreen (especially sunscreen with a low SPF) emboldened participants to spend time out in the sun that far exceeded the protective abilities of the sunscreen they were wearing. This very obviously has nothing to do with the sunscreen, and everything to do with it being used improperly. While this doesn’t necessarily mean that wearing sunscreen prevents cancer, it definitely means it doesn’t cause it!

The solution

Wear sunscreen responsibly. Don’t put it on in the morning and then spend all day in the sun and expect it to protect you like some sort of supernatural shield. Sunscreen needs to be reapplied regularly (typical recommendations are every two hours), especially if you are sweating or swimming. It isn’t invincible, and wearing it does not make you invincible, either. This is part of the reason why you can’t purchase SPF 120 sunscreens in Australia; they make the user over-confident (the Australian Therapeutic Goods Administration allows a maximum claim of SPF 50+).

aWhy Homemade Sunscreen is Never a Good Idea

Argument #2: Sunscreen contains carcinogens

The argument

One of the big draws of DIY skin care is avoiding harmful and potentially harmful ingredients found in many store bought products. Oxybenzone (a chemical UVA/UVB filter) and Retinyl palmitate (a form of vitamin A) are the two most targeted by the Environmental Working Group as being insidious.

The reality

Analysis of the study that is often referenced to prove the dangers oxybenzone (in which rats were fed oxybenzone—and we are not rats, and we aren’t eating oxybenzone) indicates “both the application regimens and time periods required to obtain systemic levels of oxybenzone equivalent per unit of body mass are essentially unattainable” (It was about 35 years of applying SPF 30 to every inch of your body every single day). The analysis also notes “in a human study, oxybenzone did not demonstrate significant endocrine disruption, even with application of a formulation containing 10% oxybenzone. In fact, after 40 years of use, we are not aware of any published study that demonstrates acute toxic effects in humans with systemic absorption of oxybenzone.”

As for retinyl palmitate, Safety of retinyl palmitate in sunscreens: A critical analysis (Steven Q. Wang, MD; Stephen W. Dusza, DrPH; Henry W. Lim, MD) concluded “there is no evidence that the inclusion of retinyl palmitate in sunscreen is photocarcinogenic in human beings,” and “retinyl palmitate in sunscreens has the same pharmacologic, biologic, and toxicologic profiles and endogenous retinyl palmitate in human skin.”

The solution

The evidence that oxybenzone and/or retinyl palmitate is harmful appears to be, at best, dubious. However, even if you aren’t convinced of the safety of oxybenzone, retinyl palmitate, or any other sunscreen ingredient, there are plenty of sunscreens available that don’t contain oxybenzone or retinyl palmitate. If you want to avoid an ingredient, there is a product on the market that caters to you. Purchase that product.

aWhy Homemade Sunscreen is Never a Good Idea

Argument #3: Sunscreen harms the environment

The argument

The ingredients in our sunscreens kill coral reefs and harm wildlife.

The reality

Some studies are showing that high concentrations of UVA/UVB filters in oceans and lakes can harm fish and coral, though at concentrations much higher than what is currently found in oceans and lakes. That’s not to say that those oceans and lakes may not reach those concentrations someday, though.

Realistically speaking, everything we do impacts our environment in some way. If you’re boycotting sunscreen to save the coral reefs, I hope you are also a raw food vegan who walks or cycles everywhere and never purchases products made more than 20 miles from your front door. We all impact our environment; try your best to make good and informed decisions, but singling out sunscreen as if it is single handedly destroying our planet is a bit ridiculous. You would likely do the earth much more good by giving up animal products, and at least there’s good data suggesting that particular change would lessen your chances of developing cancer rather than increasing them.

The solution

If you want to avoid an ingredient, there is a tested and vetted sunscreen product on the market that caters to you. Purchase that product. However, realize that everything impacts our environment, and sunscreen is not single handedly destroying our planet.

Argument #4: Sunscreen is expensive

The argument

Sunscreen is expensive. The ingredients that go into a mineral based sunscreen are inexpensive, therefore it would be cheaper to make my own.

The reality

You’re right—sunscreen is fairly expensive. When I lived in Australia I quickly realized sunscreen was going to need its own budget line as I had to apply the stuff more liberally and more frequently than I ever had to in Canada. However, it’s expensive for a reason. Sunscreen is a drug, and has to undergo extensive development and testing by real scientists in real laboratories to ensure its efficacy. Because sunscreen technology continues to develop, the price reflects the continued expense of research and development (unlike something like ibuprofen or acetaminophen/paracetamol).

As for the “it would be cheaper to make my own” part; it’s not. If you are doing it properly and having it tested for efficacy, you are looking at hundreds (if not thousands) of dollars in testing, not to mention thousands of dollars for specialized equipment (the pro grade mixer Jane mentions later on sells for over $5000!).

The ingredients may be cheap, but the rest of it definitely isn’t. Professional Cosmetic Chemist Amanda Foxon-Hill of Realize Beauty has chronicled her experiences attempting to develop her own sunscreen formula on her blog. The basic sunscreen testing she was hiring out was “$700 ish a pop”, and for me that’s got to be close to a decade of sunscreen spending! If you read her posts (linked below) it’s not hard to see how you could spend a couple lifetime’s worth of sunscreen budget on sunscreen testing and still never produce a useable end product. Amanda is a professional and has worked on sunscreen for years and still clearly finds it to be a formidable challenge.

Solution

Watch for sales (I buy mine at the end of the previous season), but this is not something you should try to reduce expenses on by making it yourself. As Amanda says “you can make sunscreen at home in as much as you don’t necessarily need any special equipment BUT you do need to get it properly tested to make sure you aren’t putting your family at risk wearing a sunscreen that is ineffective.” And that is not going to result in any sort of cost savings!

Why Homemade Sunscreen is Never a Good Idea

Argument #5: Sunscreen is overrated and unnecessary

The argument

Humans need vitamin D, and we wear so much sunscreen that we are in the midst of a vitamin D deficiency epidemic. The sun is good for you in small doses.

The reality

Recommendations vary on how much sun exposure is required to create the vitamin D our bodies need—mostly because that amount varies with your skin tone and the strength of the sun wherever you happen to be, but I’ve yet to find a recommendation higher than twenty minutes. Our bodies do not store excess vitamin D, so once you’ve had enough sun exposure to create that vitamin D, more is just unnecessary sun exposure. Depending on where you live in the world, for large parts of the year there isn’t enough UVB radiation for you to produce vitamin D, so if you are concerned about your vitamin D levels, you should be supplementing.

The solution

This is hugely dependent on where you live, your skin tone, and the season, but no dermatologist will tell you that sunscreen is completely unnecessary.

Argument #6: Sunscreen doesn’t actually prevent cancer

The argument

We can’t prove that sunscreen prevents skin cancer.

The reality

Yes, we can—at least when it comes to skin cancers caused by UVA and UVB exposure. We know that the vast majority of skin cancer is caused by damage to the DNA of skin cells, which is caused by exposure to UVA and UVB radiation. We know (thanks to expensive laboratory testing) that sunscreen reduces our exposure to UVA and UVB rays.

If you prefer more anecdotal evidence, take a look at Australia. Australia is famous for its sunny beaches, and that hole in the ozone layer than means the Australian sun is effectively supercharged. According to Cancer Council Australia:

  • Australia has one of the highest rates of skin cancer in the world… the majority of skin cancers in Australia are caused by exposure to UV radiation in sunlight.
  • Sunburn causes 95% of melanomas, the most deadly form of skin cancer.
  • Approximately two in three Australians will be diagnosed with skin cancer by the time they are 70
  • The incidence of skin cancer [in Australia] is one of the highest in the world, two to three times the rates in Canada, the US and the UK

More sun, more skin cancer. Growing up in Canada, most of the cancer prevention advertising I was exposed to was targeted at smoking; when I moved to Australia, it was all about sun exposure.

The solution

UV rays cause skin cancer, and good sunscreens prevent/reduce exposure to those rays.

Why Homemade Sunscreen is Never a Good Idea

Argument #7: But my recipe works!

The argument

I made a sunscreen and I wear it all the time on myself/my family and it works!

The reality

Have you had it professionally tested? If you haven’t, you don’t know if it works. UVB rays are what causes burns, so while you may be able to say with some certainty that you aren’t burning, you have no idea if you are protecting against UVA rays, and those are the rays that cause invisible (and insidious) damage.

Sunscreen is way harder to make than laypeople think. And I get it—I do. You look at an ingredient list on a mineral sunscreen and everything looks familiar. You’ve got zinc oxide and titanium dioxide! You’ve made diaper cream before, how different can sunscreen be? It’s the same ingredients, so that means it’s the same—right?

Jane Barber sums up the challenges very well in this post originally from her educational cosmetic formulation discussion group (shared here with permission):

Sunscreen is one of the most difficult products a chemist can be asked to formulate. It takes many years of training for a chemist to be familiar with how to formulate this type of product but even so they cannot predict what SPF it will have. As you will see from the list below, formulating sunscreen is extremely complex and requires expensive testing so it is not advisable for homecrafters to make:-

  1. To be effective the sunscreen needs to cover both UVA and UVB – it must be “broad spectrum”. In order to achieve this varying combinations of UV filters are used. The filters chosen must be:
  • properly solubilised (usually achieved through the use of esters known for this property with a sufficiently high oil phase). Crystallisation of solid organic filters can occur which reduces SPF, stability and sensory of the formula. Chemists run tests to ensure it does not recrystallize over time.
  • not react with the other ingredients in your formula
  • be photostable and not degraded
  • be within legal limits. (Also, some UV filters used in the EU aren’t permitted in the USA).
  • be homogeneously and evenly dispersed throughout the emulsion which, especially for zinc oxide is very challenging even with a Silverson lab homogeniser
  • zinc oxide is incompatible with many ingredients we use in our emulsions, it also tends to migrate thereby increasing pH and forming alkaline Zn complexes and agglomeration resulting in significantly reduced SPF and instability.
  • the right ratio of UVA and UVB filters needs to be chosen for the sunscreen to be broad spectrum
  1. Emulsifiers, thickeners, emollients (and polarity), film formers in the formula will affect the end SPF so these must be chosen carefully. Chemists should be aware of which ingredients in these categories are appropriate to use. In addition some preservatives are deactivated by UV filters
  2. An even film over the skin is needed in order for the UV filters to be effective so application thickness, spreadability, absorption and emulsion size also affects SPF.
  3. With all the above variables, it is impossible even for a chemist to predict the end SPF as it is so complex. The product must be sent for various tests in order to determine the end SPF.
  4. Lastly, sunscreen is classed as a drug in the USA – the relevant FDA monograph needs to be followed.

The solution

Unless you have had your formula professionally tested, you have no idea if it works, and the fact that it seems to work on you is functionally useless.

Making your own sunscreen is like assuming mouldy bread is the same thing as penicillin because they’re both mold (“Saprophytic species of Penicillium and Aspergillus are among the best-known representatives of the Eurotiales and live mainly on organic biodegradable substances. Commonly known in America as molds, they are among the main causes of food spoilage, especially species of subgenus Penicillium.” [source]), and then trying to treat your pneumonia with some fuzzy leftovers you dug out of the back of your fridge. We derive penicillin from Penicillium, so why don’t we all skip the pharmaceutical companies and eat moldy food when we feel sick? Because we know it’s not the same. Ditto for DIY sunscreen. It is so much more than the sum of its parts.

In conclusion

Sunscreen is not the be all and end all of sun protection, and I’m not trying to suggest that it is. Make use of hats, clothes, shade, and sunglasses. Stay out of the sun during the hottest part of the day. Don’t intentionally tan. Yes, some sun exposure is good, but it really doesn’t take much to produce the amounts of vitamin D our bodies require.

Sunscreen shouldn’t be your entire sun protection plan, but it should be part of it. There is no reason for it not to be, and so many reasons to use it. Whether you want to look young for decades (Nicole Kidman famously won’t cross the street without putting on a hat and her skin still looks 18) or don’t want to develop skin cancer, sunscreen will help. And, even if you still don’t want to wear sunscreen, don’t make your own. It’s better for you to know you aren’t wearing sunscreen and act accordingly (like the people in the Swedish study) rather than be overly confident wearing your ineffective DIY stuff.

Like many things, sunscreen is so much more than the sum of its parts. Making sunscreen is a complex, highly variable process that is best left to the experts. Thankfully, there are dozens (if not hundreds) of different professionally made and vetted sunscreens on the market, so no matter what ingredients you may be trying to avoid, or whatever price you’re trying to pay, there’s a sunscreen for you!

Why Homemade Sunscreen is Never a Good Idea

Further Reading & Viewing

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