5 Reasons why you should not make Homemade Sunscreen - Formula Botanica (2024)

If you love DIY beauty then at some point you might have investigated making your own homemade sunscreen. We want to show you in this blog post that DIY sunscreen is an all-round bad idea. We don’t teach our students how to make sunscreen formulations in our courses for exactly the 5 reasons we describe below.

Making sunscreen can divide whole rooms of formulators. It is understandable that some people want to be able to make their own homemade sunscreen as they raise concerns about the chemicals used in mainstream sunscreens. However, many formulators also understand that making sunscreens will require expensive and extensive research and testing.

Once you start to investigate homemade sunscreens on the internet, you’ll find a huge array of different recipes that range from using basic oils to the use of ingredients such as zinc oxide and titanium dioxide.

We previously blogged about why you should not use coconut oil as a sunscreen, but we now want to take that one step further and explain that all homemade sunscreen is a bad idea – unless you are prepared to undertake extensive testing to back up your claims.

How do sunscreens work?

Sunscreens are formulations used to mitigate or alleviate the adverse effects of ultraviolet radiation on skin, which is the most important avoidable cause of skin cancer.Sunscreens can be made using inorganic and organic filters, that work to reflect or absorb UV radiation.

The most commonly used inorganic ingredients, also referred to as physical or mineral agents, are Zinc Oxide (ZnO) and Titanium Dioxide (TiO2). These two ingredients are also most commonly found in homemade sunscreen recipes found online.

Inorganic sunscreens work by creating an armour on the surface of the skin, which reflects and scatters UV rays. The effectiveness of this kind of sunscreen is totally dependent on the film formation on the skin, which must be completely even for a good protection.

Organic, or also called chemical sunscreens, work mostly by absorbing the sun’s rays. These ingredients must be photostable and well stabilised in the formulation to be active. Chemical sunscreens are the ingredients that are more likely to cause allergic reactions and are usually more irritating to the skin, which is why physical ingredients are mainly found in homemade sunscreen recipes.

UV Rays & SPF

Regardless of whether it is organic or inorganic, in order to be effective a sunscreen should be broad spectrum, which means it will filter both UVA and UVB rays, which are both responsible for the detrimental effects of solar radiation on skin.

Whereas UVB is believed to interact directly with DNA to initiate signature mutations of basal and squamous cell carcinomas, UVA wavelengths are believed to interact indirectly, inducing the production of free radicals that may indirectly damage DNA and cause protein damage, which contributes to photoaging.

One of the most important measurements for a sunscreen’s activity is the SPF. SPF stands for Sun Protection Factor, and it is an internationally accepted standard, by which the efficacy of sunscreens is assessed, and it is a relative measure of how long a sunscreenwill protect you from UVB rays.

Challenge 1: Effectiveness

Your sunscreen needs to be effective to protect yourself from sunburn and premature photo ageing (enrol for our Certificate in Organic Anti-Ageing Skincare to learn how to make formulations that help the skin age gracefully). Sunscreens need to work the same way for everyone. They must be applied evenly on the skin and be effective regardless of weather conditions, over time of application and during the sunscreen formulation’s shelf life.

When you make a homemade sunscreen, you won’t know its effectiveness unless you test it in a lab.In short:

• You start out by deciding what SPF you want to achieve. You then choose the correct SPF blocker in order to get to that level.
• The sunscreen is then tested in the lab multiple times during the development process to ensure that the SPF is still on track.
• The sunscreen is then tested on human volunteers who are exposed to a specific amount of sunlight. Their skin reaction is then assessed.
• The lab then compares these results with their test results to ensure the SPF matches.

The effectiveness of your sunscreen formulation must be proved and measured by parameters that will assure you that it is performing as it should. Otherwise, you are flying blind. Guessing the effectiveness of your sunscreen by subjectively looking at your skin is not accurate and it doesn’t prove that your formulation is effective. And remember, the redness of the skin is mostly related to the UVB rays. Only a lab test will prove if your homemade sunscreen is effective.

Challenge 2: Time of Exposure

Once you lie in the sun for a while without sunscreen, your skin will start to turn red. This is known as erythema or sunburn. The SPF of your sunscreen provides an indicator for how long you can safely stay in the sun; it tells you about your formulation’s ability to delay the skin turning red (induced by solar radiation).

If you don’t know what your SPF measurement for your homemade sunscreen, how do you know how long you can safely stay in the sun?

Even if you decided to stay out in the sun until your skin turned red in order to determine what your formulation’s time of exposure is, it would generally be too late by the time you find out – erythema can occur 6-24 hours after exposure to the sun. Furthermore, your skin type plays a role in the timing and intensity of erythema too.

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Challenge 3: Formulation Challenges

Even if you have experience in making formulations, it is still likely that your homemade sunscreen will still not work. You can put on your lab coat and give it your best go in the lab, but even the most experienced formulators still find themselves going back to the drawing board when it comes to SPF.

Your SPF is affected by all of the ingredients in your formulation as well as the manufacturing technique you use.Not only is proper dispersion of sunscreen agents important – which is only achieved with professional lab equipment – but the whole composition of the formula also affects the SPF.

Inorganic sunscreen agents have a tendency of clumping in your formulation which can have a detrimental affect on your SPF – it might lower significantly in one place, whilst causing high spots in others. Furthermore, some emulsifiers, stabilisers and certain additives can reduce the SPF.

So you see that even the most experienced formulators will struggle to guarantee that their sunscreen filters are evenly dispersed, do not interact with other ingredients, are photostable and provide broad spectrum coverage.You would need to evaluate pH interaction and find a preservation system that works too. As you can imagine, this is a financially challenging process, where you will be probably burning both your money and your skin.

Challenge 4: Stability

Oxidation, degradation, preservation, clumps. These challenges face all cosmetic formulators (and we cover stability in great detail in our Certificate in Cosmetic Stability Testing). When it comes to sun exposure, dealing with stability is even more important.

Zinc Oxide and Titanium Dioxide are reactive ingredients, so it is not possible to guarantee that the dispersion of these ingredients will be stable over time in a homemade sunscreen. Zinc oxide for instance, is a strongly charged particle and tends to form clumps. You won’t be able to spot these clumps in your formulation either as they are usually invisible to the naked eye.

Remember that sunscreens are intended to be exposed to sunlight, and the ingredients contained in the formula need to be stable – not only whilst inside your sunscreen’s packaging, but also whilst on the skin. For that reason, you will also need to be sure of your ingredients’ photo stability and interaction with each other.

Challenge 5: Safety

By now, you’ve probably figured out that if your sunscreen is not perfectly made, with all the sunscreen ingredients evenly dispersed and stabilised, you will most likely not achieve even protection on your skin.

If you are not yet convinced by the technical challenges of making homemade sunscreen, we’ve included some stats skin cancer that will hopefully help you decide to ditch your homemade sunscreen recipes for good:

• Ultraviolet (UV) radiation is a proven human carcinogen.
• On average, a person’s risk for melanoma doubles if he or she has had more than five sunburns.
• The Skin Cancer Foundation states that about 90% of non-melanoma skin cancers are associated with exposure to ultraviolet (UV) radiation from the sun.
• Over the past three decades, more people have had skin cancer than all other cancers combined.
• The vast majority of melanomas are caused by the sun. In fact, one UK study found that about 86 percent of melanomas can be attributed to exposure to ultraviolet (UV) radiation from the sun.
• An estimated 90 percent of skin aging is caused by the sun.
• Also note that the lag time between exposure and tumor diagnosis for melanoma is two decades or more.

We should also mention the compensation hypothesis here which shows that people tend to compensate for the use of sunscreen by increasing their time in the sun, i.e. the sense of the security given to them by sunscreens encourages longer sun exposure. For that reason, uneven protection is even more dangerous.

The Verdict: Ditch the Homemade Sunscreen

Sunscreen use is and will remain a subject of controversy. However, we can hopefully all agree that sun protection is important and that its use improves our chances of not getting skin cancer.

Many issues regarding sunscreen formulations have yet to be resolved, that is a fact, but remember that sunscreen should be just one of the sun protection strategies you use to protect your skin. While you are out in the sun protect yourself by wearing clothes, avoiding excessive sun exposure and choosing a sunscreen that you trust. We strongly encourage you to ditch the homemade sunscreen.

References

1. International Agency for Research on Cancer: IARC Monographs on the Evaluation of Carcinogenic Risks to Humans: Solar and Ultraviolet Radiation, vol. 55. Lyon, France: International Agency for Research on Cancer; 1992.
2. Weinstock MA: Epidemiology of ultraviolet radiation. In Cutaneous Oncology: Pathophysiology, Diagnosis, Management. Edited by Miller SJ, Maloney ME. Malden, MA: Blackwell Science; 1998:121–128.
3. General: Título:SunscreenFonte:Current opinion in oncology [1040-8746] Weinstock, A yr:2000 vol:12 iss:2 pg:159 -162
4. Dangerous: Sunscreen Use and Duration of Sun Exposure: a Double-Blind, Randomized Trial Autier, Philippe ; Dor, Jean – Franois ; Ngrier, Sylvie ; Linard, Danile ; Panizzon, Renato ; Lejeune, Ferdy J ; Guggisberg, David ; Eggermont, Alexander M. M Journal of the National Cancer Institute, 1999, Vol.91(15),
5. Guidelines for SPF tests: FDA guidelines and EU standard tests.
6. Wang & Lim, 2016. Principles and Practice in Photoprotection.
7. Skin Cancer Foundation, Facts & Statistics.

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