How to formulate sunscreen: an overview

Is a sunscreen a cosmetic (or drug)?

Before we take you through some basic sunscreen formulation fundamentals, it is also important to check whether sunscreen products are regulated as cosmetics or drugs in your region. Where a product is regulated as cosmetics, ensuring compliance is significantly easier than where it is regulated as a drug or therapeutic good. Where regulated as a drug or therapeutic good, there are considerable extra steps in registration, compliance and even manufacture, including large minimum order quantities, which may make the addition of a sunscreen too difficult for many small brands.

For a quick overview, watch our video: Should your cosmetic brand have a sunscreen product?

There are also additional rules over ‘water resistance’ claims, warnings and certain label information required with all sunscreen products. Before you place a sunscreen product onto the market, make sure your brand has checked and achieves all of these compliance requirements otherwise you will need to remove it.

Here is an overview of how different countries regular products with SPF claims:

When do you need to conduct SPF testing?

Let’s be extremely clear here: if your brand is claiming an SPF on the label and/or in the promotion of the product, the answer is ALWAYS.

Don’t be fooled by what you might hear or read. The fact is: the brand putting the SPF product into the marketplace is responsible for holding direct evidence of the SPF claimed for their specific product/formula.

We do get a lot of small brands contacting us because they read or hear things that confuse them about sunscreen regulations – but if they were to follow the misinformation, they would land in a lot of hot water with the regulators. We don’t want to see you compromise your brand – especially if you are small and starting out – so here are common misconceptions we hear, and the truth, so you can make the right choices for your brand:

Myth: but I’m a small brand, I thought I was exempt from some of these rules.

• Fact: If you are promoting your product as containing any sort of SPF or sun protection, then your brand, regardless of size, is responsible for holding appropriate SPF evidence as required by the country the product is marketed in.

Myth: I’m getting the product contract manufactured, so they have to take care of compliance, don’t they?

• Fact: It is the Brand (not the manufacturer) who puts the product onto the market that is responsible for ensuring all compliance requirements are met for sunscreens, including holding evidence for the SPF claimed on the label/in any advertising.

Myth: I’m using a formula provided by a Chemist/supplier, and they have stated the SPF, so I don’t need to conduct testing.

• Fact: Even if you are using a formula provided by someone else, regardless of whether that formula was free or paid for, the final responsibility for holding the evidence to support that SPF rests with the Brand putting the product onto the market.

Myth: my formula contains plant oils with natural SPF protection, so I don’t need to get it tested.

• Fact: natural oils don’t provide significant SPF protection. In any case, any SPF claim still needs to be verified with the correct testing and evidence. Watch this video where we show you the SPF results of natural oils reputed to have UV protection: Natural oils and sun protection.

SPF testing to specific standards are required in different regions of the world; not just any testing will be accepted. Make sure you are fully aware of the types of tests required and costs of SPF testing specific to the country where you will be selling your sunscreen.
 

Organic and inorganic UV filters: which is best?

There are two types of sunscreen agents:

• organic sunscreens:
  • commonly referred to as chemical sunscreen agents; they are named organic sunscreen ingredients because they conform to organic chemistry principles. These materials are NOT permitted in natural or organic sunscreen formulas.
  • work by absorbing UV light.
  • common examples include ethylhexyl methoxycinnamate (also known as octyl methoxycinnamate); benzophenone-3, ethylhexyl salicylate and homosalate.
• inorganic sunscreens:
  • commonly referred to as natural sunscreen agents; they are named inorganic because they conform to inorganic chemistry principles. These materials ARE permitted in natural and organic sunscreen formulas but are NOT actually all natural.
  • may also be referred to as physical sunscreen agents, because they work by reflecting or scattering UV light, providing a physical barrier to UV entry to the skin.
  • common examples include zinc oxide and titanium oxide.

The best performing sunscreens tend to incorporate both organic and inorganic sunscreen agents with the addition of waterproofing ingredients. This usually provides long lasting protection from UVA and UVB rays through absorption and reflection of UV light, whilst being resistant to easy wash off from perspiration and swimming.

The best skin feel is often achieved by using organic sunscreens alone, as inorganic sunscreens come in a powder form only. Inorganic sunscreens may be coated to help improve skin feel and spread, but careful sunscreen formulation is often required to ensure stability and a comparable light feeling.
 

Why are combinations of sunscreen agents used in a sunscreen formula?

The combination of organic and inorganic sunscreen agents typically achieves a ‘synergy’ whereby a higher SPF and UVA rating can be achieved from using less total UV filters, achieving better stability in the end product and vastly improved skin feel during application and wear for consumers.

Additionally, there are strict limits over the types and amounts of sunscreen agents that can be used in a sunscreen formula. This means you can’t usually achieve the required SPF without combining at least a few sunscreen agents.

Finally, UV filters have different wavelengths of absorbance or transmittance, which means they will protect against certain wavelengths of light in the UVA or UVB spectrum. To provide broad spectrum protection, UV filters must cover a large amount of the UVA and UVB spectrum, otherwise they are not providing adequate protection.

For example, this is the protection spectrum of Escalol 517 (INCI: Butyl Methoxydibenzoylmethane):

Image: Courtesy of Ashland

In this graph you can see:

• the maximum wavelength of absorption is 357nm – it is a UV absorber at this wavelength, but provides very little protection at 330nm or below. 
• using sunscreens with only one or two small peaks in the UVA and UVB spectrums will not provide suitable UV protection.

A combination of sunscreens that provide peaks in various places, over the wavelength range of 290 to 400nm is required to be considered broad spectrum and truly protective.
 

It takes more than just the sunscreen agents to achieve a good SPF

The most important aspect of a sunscreen product is undoubtedly the way the formula has been constructed. Even if you have a great choice of sunscreen filters in the formula, the SPF performance will be affected by:

• the way the product spreads: a smooth, even film on the skin provides the best SPF rating.
• product stability: if the base formula starts to separate or form lumps over time, application will not enable an even spread of the sunscreen ingredients.
• compatibility: UV agents cannot be allowed to agglomerate or crystallise over time, so they need a compatible formulation base to ensure a great shelf life.

To help you understand this principle, consider these images:

Both of these diagrams use the same quantity of incidental UV light (the arrows) and representative UV filters (the ovals). The image on the left provides an example of when UV filters agglomorate, thus allowing a lot of incidental UV light to pass through, resulting in a low SPF. The image on the right shows the same number of ovals, but in an even spread, to catch the most incidental UV light.  

In reality, a combination of UV filters is commonly used for reasons previously explained. In an even spreading, compatible and stable base formula, it could be represented like this:  

How to create sunscreen formulas: step-by-step guide

Before we take you through a step-by-step guide of how to formulate suncreens, remember that:

• sunscreen formulas have strict regulatory limits over the types and amounts of sunscreen, and often other ingredients, that may be used;
• SPF testing to local country requirements is essential for any product claiming SPF/sun protection; and
• the base formula must be stable, spread well and compatible with the choice of UV agents.

If you don’t know how to check or achieve any of the above requirements, then you should leave formulating sunscreens to a Cosmetic Chemist, or learn properly, with our Certificate in Advanced Cosmetic Science or Diploma of Personal Care Formulation.

Then, you are ready to complete the steps to formulate a sunscreen:

1. Determine UV filters and input amounts required to achieve the required SPF (in theory)
   • Check all inputs comply with local country regulations and provide broad spectrum UV protection.
2. Determine suitable lipids to ensure compatibility and even spread of the UV filters.
3. Add the lipid soluble UV filter input + selected lipids to determine the total lipid input. This will determine if your formula is likely to be w/o or o/w. Note: there is usually a significant oil + oil soluble component, which is why most sunscreens with high SPF are w/o emulsions.
4. Select the emulsifiers + polymers to stabilise the UV filters and suit the emulsion type (usually w/o emulsion).
   • Check all inputs comply with local country regulations and are compatible with the selected sunscreen ingredients.
5. Add compatible film formers for water resistance.
6. Double check the formula for stability and compatibility, remembering a stable emulsion with good spread helps yield the best possible SPF.

Then you are ready to source your materials and start preparing samples!

Be prepared to revise your formula and make more samples until you get a suitably light and long spreading formula that feels great and performs well. And of course, remember to get the right SPF tests conducted to suit the countries where the product will be sold.

Happy formulating!