What are the ingredients of a sunscreen cream?

A common supplement to other forms of photoprotection (sun hats, long UV-protective clothing, parasols, etc.), the sunscreen is a topical product designed to effectively protect the skin from all potential damage from UV rays (sunburn, hyperpigmentation, premature photoaging of the skin, melanoma, squamous cell carcinoma, etc.). Classified more as drugs in some countries (United States and Canada), its formulation is a complex science due to the requirements and restrictions imposed.

In addition to significant regulations that limit both the type and quantity of sun protection agents that can be used, the base formula must be carefully formulated to stabilise these materials, and maintain a high level of performance and consistency over an appropriate shelf life. Indeed, the challenge is to achieve a water-in-oil (W/O) type reverse emulsion that is as stable as possible and ensures optimal sun protection, while guaranteeing sensory qualities that will encourage uniform application of the product on the skin. But what should sunscreen be made of?

20% of sun filters.

Adequate protection that covers both UVA and UVB rays helps to prevent skin cancers, protect against sunburn, and slow down the formation of wrinkles, the development of brown spots and the loss of elasticity. To achieve this, sun care products derive their effectiveness from the UV filters they contain, dissolved or dispersed in a mixture of other ingredients, such as water, oils, moisturisers and antioxidants. Their role is to prevent the harmful ultraviolet rays of the sun from reaching the skin.

All sunscreen filters used fall into one of the following two categories: organic (chemical) filters and mineral (physical) filters, which are distinguished by their origin. Most sun creams on the market employ a combination of several UV filters, as each sunscreen filter offers different protection across the entire range of UV wavelengths.

As of today, the European Union authorises 28 sun-filtering ingredients, whereas only 17 are approved by the United States (FDA).

• The physical filters, which utilise inorganic compounds as active ingredients (zinc oxide and titanium dioxide), work by forming a physical protective barrier on the skin's surface, responsible for the often observed white tint, to reflect/disperse (about 5%) and primarily absorb solar radiation (about 95%) and dissipate it in the form of heat;

• Chemical filters, which are often aromatic molecules conjugated with carbonyl groups, only act by absorbing high-energy UV rays and releasing them as harmless thermal energy for the epidermis. However, concerns have emerged regarding the toxicity and mutagenicity of certain chemical UV filters, which warrant further evaluation. Moreover, some of them have been banned in places like Hawaii, Florida, and the American Virgin Islands due to their impact on aquatic life and the environment.

In our sun creams, we primarily use mineral filters and four chemical sun filters, which have been rigorously selected for their safety for health and the environment, in order to ensure adequate coverage of the UVA and UVB range and provide broad-spectrum protection.

55% of formula stabilisers.

The majority consists of solvents, which are typically water and also oils.

Although they do not block the sun's rays, other ingredients in sun creams help UV filters to remain in solution and not degrade. Provided in the form of dry powder or pre-dispersed in oil or aqueous bases, sun filters are distributed in the appropriate phase or added to the product once the emulsion is formed. However, this mixture can encounter problems. For instance, agglomerates can form and have a negative impact on the SPF. Therefore, the emulsion must be completely stable.

To achieve this, the addition of emulsifiers, thickeners, chelating agents, pH regulators, antioxidants, and stabilising agents is necessary to obtain a homogeneous, functional solution that is easy to spread. However, these should not be used in excess as certain additives can reduce the SPF. Preservatives, such as thedehydroacetic acid or o-cymen-5-ol, are also present in the formulas. They prevent the active ingredients from breaking down and/or extend the product's shelf life.

23% sensory amplifiers.

The effectiveness of sunscreen also depends on the quality of the formulation. Indeed, certain ingredients contained in sunscreens can alter the sensation or smell of the product. To counteract this, fragrances and emollients are used, which are elements that can affect the sensation on the skin. Without them, the sunscreen would be grainy, overly greasy and difficult to spread if it only contained UV filters.

To minimise the risk of allergies or irritations, our sun creams are free from fragrances and essential oils, thus making them suitable for pregnant and breastfeeding women.

2% of other active ingredients.

Beyond sun filters, other types of active ingredients can be incorporated into the composition of sun creams, such as humectants or anti-radicals. Furthermore, in addition to reducing the overall burden of free radicals produced by exposure to sunlight that reach the skin, the addition of certain antioxidants can act synergistically when combined with UV filters to positively impact the overall SPF value and thus enhance the photostability of the active ingredients.

In addition to the photoprotective benefits provided by sun filters, our facial sun creams containhyaluronic acid (INCI Hydrolyzed Hyaluronic Acid) in their formula, while our body sunscreens containaloe vera (INCI: Aloe Barbadensis Leaf Juice Powder) to also offer moisturising properties.

• CASWELL M. Sunscreen formulation and testing. Allured’s Cosmetics & Toiletries (2001).