I’ve been asked many times to formulate a Roodt sunscreen balm/ lotion.

The following article will explain why I won’t be formulating any kind of sunscreen/sun barrier lotion or balm.

Bear with me its a long but awesome read



Sunscreens are formulations used to mitigate or alleviate the adverse effects of ultraviolet radiation on the 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 sunscreen recipes.

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

Organic, or also called chemical sunscreens, work mostly by absorbing the sun’s rays. These ingredients must be photostable and well stabilized 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 sunscreen recipes.


Regardless of whether it is organic or inorganic, to be effective 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 the 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 sunscreen will protect you from UVB rays.



Your sunscreen needs to be effective to protect yourself from sunburn and premature photo-aging Sunscreens need to work the same way for everyone. They must be applied evenly on the skin and be effective regardless of weather conditions, overtime of application, and during the sunscreen formulation’s shelf life.

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

You start by deciding what SPF you want to achieve. You then choose the correct SPF blocker 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 the 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 sunscreen is effective.



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 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 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.



Even if you have experience in making formulations, it is still likely that your sunscreen will still not work. You can put on your lab coat and give it your best to 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 effect on your SPF – it might lower significantly in one place, whilst causing high spots in others. Furthermore, some emulsifiers, stabilizers, 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.



Oxidation, degradation, preservation, clumps. These challenges face all cosmetic formulators. 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’ photostability and interaction with each other.



By now, you’ve probably figured out that if your sunscreen is not perfectly made, with all the sunscreen ingredients evenly dispersed and stabilized, 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 on 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



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 untested sunscreen


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.

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.

General: Título: Sunscreen Fonte: Current opinion in oncology [1040-8746] Weinstock, A yr:2000 vol:12 iss:2 pg:159 -162

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),

Guidelines for SPF tests: FDA guidelines and EU standard tests.

Wang & Lim, 2016. Principles and Practice in Photoprotection.

@Skin Cancer Foundation, Facts & Statistics.

Formula Botanica”



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