In this article about sunscreen products you will learn about how sunscreen products work, the types of sunscreens, their ingredients, formulation, regulation and claims.
Mechanism of action of Sunscreen Products
Sunscreens, also referred to as sun protectants, play a crucial role in mitigating the effects of ultraviolet (UV) radiation on human skin. The efficacy of sunscreens is primarily determined by their ability to absorb, reflect, or scatter UV radiation, thereby preventing DNA damage and subsequent photoaging, sunburn, and carcinogenesis. Sunscreens are formulated with a combination of organic (chemical) and inorganic (physical) UV filters, each exhibiting distinct mechanisms of action.
Organic/Chemical UV Filters
Organic UV filters, such as avobenzone, octocrylene, and octinoxate, function by absorbing high-energy UV photons and converting them into lower-energy heat. These molecules typically contain conjugated π-electron systems, allowing them to absorb UV radiation within specific wavelengths, particularly UVA (320-400 nm) and UVB (290-320 nm). Upon exposure to UV light, organic filters undergo a photochemical reaction, transitioning from a ground state to an excited state. The absorbed energy is dissipated as heat, effectively preventing the penetration of harmful UV rays into the skin.
Octinoxate absorbs UVB radiation with a peak absorption at 310 nm, making it effective in preventing erythema and DNA photodamage. Similarly, avobenzone, a widely used UVA filter, absorbs across the UVA spectrum, offering broad-spectrum protection.
Despite their efficacy, organic UV filters are susceptible to photodegradation, which can result in reduced protection over time. To mitigate this, stabilisers like octocrylene are often incorporated into formulations to enhance photostability.
Inorganic/Mineral UV Filters
Inorganic UV filters, such as titanium dioxide (TiO₂) and zinc oxide (ZnO), offer a distinct mechanism of action by physically reflecting and scattering UV radiation. These filters form a physical barrier on the skin’s surface, reflecting both UVA and UVB radiation. The scattering of photons is particularly effective against UVB wavelengths, whereas absorption also occurs in the UVA range due to the semiconductor properties of these metal oxides.
The particle size of inorganic filters significantly influences their efficacy and cosmetic acceptability. For example, nano-sized titanium dioxide and zinc oxide provide effective UV protection without the visible whitening effect associated with larger particles. These nanoparticles, typically ranging from 20 to 100 nm in diameter, maintain the protective properties of their larger counterparts while enhancing transparency and user compliance.
Synergistic Effects and Photostability
In many commercial sunscreen formulations, a combination of organic and inorganic filters is utilised to achieve broad-spectrum protection. The synergy between these filters not only expands the protective range but also improves the overall photostability of the product. For example, formulations combining avobenzone (a UVA filter) with octocrylene (a photostabilizer and UVB filter) provide enhanced long-term protection against both UVA and UVB radiation.
Additionally, recent advancements have explored the incorporation of film-forming polymers and encapsulation technologies (e.g., liposomes or silica-coated particles) to further enhance the stability and longevity of sunscreens under real-world conditions, such as exposure to water and perspiration.
Types of Sunscreen Products
Primary Sunscreens
Primary sunscreens are products whose main purpose is to protect the skin from UV radiation. They are formulated specifically to provide broad-spectrum protection against UVA (320-400 nm) and UVB (290-320 nm) rays, helping to prevent sunburn, skin damage, and photoaging. These sunscreens typically contain active UV filters and are subject to strict regulatory requirements due to their primary protective role.
Examples of primary sunscreens include lotions, creams, sprays, and gels marketed explicitly for sun protection, such as broad-spectrum SPF 30 sunscreen lotions or SPF 50 sprays for outdoor activities.
Secondary Sunscreens
On the other hand, secondary sunscreens are products that have other primary functions but include UV protection as an additional benefit. These products are primarily designed for purposes such as moisturising, makeup, or anti-aging but are formulated with UV filters to provide some level of sun protection.
Common examples of secondary sunscreens include moisturisers with SPF, foundations with sun protection, and BB creams. These products are designed for daily wear and provide convenience by combining cosmetic benefits with sun protection.
Ingredients in Sunscreen Products
The below is a table of ingredients permitted in sunscreen products in the USA, these are the most common ingredients found in primary and secondary sunscreens.
| UV Filter | Protection | Chemical Structure | Max% | Other names |
|---|---|---|---|---|
| Titanium Dioxide* | Broad spectrum |  | 25 | Titanium Dioxide |
| Zinc Oxide* | Broad spectrum |  | 25 | Zinc Oxide |
| Avobenzone* | Broad Spectrum |  | 3 | Butyl Methoxydibenzoylmethane |
| Para-aminobenzoic acid | UVB |  | 15 | Amino benzoic acid |
| Cinoxate | UVB |  | 3 | 2-ethoxyethyl-p-methoxycinnamate |
| Dioxybenzone | UVB & UVAII |  | 3 | Benzophenone-8 |
| Homosalate* | UVB |  | 15 | Homo methyl salicylate |
| Meradimate | Broad spectrum |  | 5 | Menthyl anthranilate |
| Octocrylene* | UVB & UVAII |  | 10 | Octocrylene |
| Octyl methoxycinnamate* | UVB |  | 7.5 | Ethylhexyl Methoxycinnamate |
| Octyl salicylate* | UVB |  | 5 | Ethylhexyl Salicylate |
| Oxybenzone* | Broad Spectrum |  | 6 | Benzophenone-3 |
| Padimate O | UVB |  | 8 | Ethylhexyl Dimethyl PABA |
| Ensulizole | UVB |  | 4 | Phenylbenzimidazole sulfonic acid |
| Sulisobenzone | Broad spectrum |  | 10 | Benzophenone-4 |
| Trolamine salicylate | UVB |  | 12 | TEA salicylate |
Formulation of Sunscreen Products
Sunscreen cream/lotion
Ingredient | Maximum concentration (% w/w) |
Oils, waxes and fats | 70 |
UV filters | 40 |
Silicones(including volatile silicones) | 30 |
Humectants | 30 |
Ethanol (alcohol, alcohol denat.) | 25 |
Emulsifying agents | 10 |
Bulking agents | 10 |
Additional ingredients | 6 |
Film forming polymers | 5 |
Thickeners | 5 |
Parfum | 3 |
Preservatives, antimicrobials | 2 |
Colourants | 2 |
Aqua | to 100 |
Ingredient Types and functions in sunscreen creams/lotions
Oils, Waxes, and Fats – 70%
These form the base of the lotion, providing texture and emollience. They help with skin hydration and create a barrier to lock in moisture. Examples: Vegetable oils (e.g., coconut oil, almond oil), mineral oils, and long-chain alcohols like cetyl alcohol.
UV Filters – 40%
UV filters protect the skin from harmful ultraviolet radiation by either absorbing, reflecting, or scattering UV rays. Examples: Chemical filters like avobenzone and octocrylene; physical (mineral) filters like zinc oxide and titanium dioxide (nano).
Silicones – 30%
Silicones enhance spreadability, create a smooth feel, and provide water resistance to the formulation. Examples: Cyclopentasiloxane, dimethicone.
Humectants – 30%
These ingredients attract and retain moisture in the skin, preventing dryness. Examples: Glycerin, propylene glycol.
Ethanol – 25%
Ethanol is used as a solvent to improve texture and help in the quick evaporation of the product, giving a lighter feel.
Emulsifying Agents – 10%
These help blend water and oil components, creating a stable and consistent lotion. Examples: Glyceryl stearate, PEG-100 stearate.
Bulking Agents – 10%
Bulking agents add volume and enhance texture without contributing to the active properties of the product. Examples: Talc, silica, nylon powder.
Additional Ingredients – 6%
These provide extra benefits such as soothing, anti-inflammatory properties, or added skin nourishment. Examples: Bisabolol (from chamomile), vitamins (like vitamin E).
Film Forming Polymers – 5%
These create a protective film on the skin, increasing the sunscreen’s durability and water resistance. Examples: PVP (polyvinylpyrrolidone).
Thickeners – 5%
Thickeners adjust the viscosity of the lotion, making it easier to apply and enhancing its stability. Examples: Carbomer, xanthan gum.
Parfum – 3%
Fragrances are added for a pleasant scent, though they are kept minimal in sunscreens to avoid irritation.
Preservatives, Antimicrobials – 2%
These protect the product from microbial contamination, ensuring a longer shelf life.
Examples: Phenoxyethanol, parabens, ethylhexylglycerin.
Colourants – 2%
Colourants give the product its colour, although sunscreens typically contain minimal amounts to avoid altering skin tone. Examples: Iron oxides.
Aqua – To 100%
Water is the solvent used to dissolve other ingredients and create the lotion’s base.
Sunscreen Oil
Ingredient | Maximum concentration (% w/w) |
Ethanol (alcohol, alcohol denat.) | 70 |
UV filters | 35 |
Silicones(including volatile silicones) | 30 |
Film forming agents | 10 |
Additional ingredients | 6 |
Parfum | 3 |
Colourants | 2 |
Thickeners | 1 |
Preservatives, antimicrobials | 1 |
Oils | to 100 |
Ingredient Types and functions in sunscreen oils
Ethanol – 70%
Ethanol (or alcohol) acts as a solvent and helps to create a lightweight, fast-drying formulation. It evaporates quickly, leaving behind active ingredients. Examples: Alcohol denat.
UV Filters – 35%
UV filters protect the skin by absorbing, reflecting, or scattering harmful UV rays, helping prevent sun damage. Examples: Avobenzone, octocrylene, octinoxate.
Silicones – 30%
Silicones enhance the spreadability of the product and add a silky feel. They also provide water resistance, helping the sunscreen last longer on the skin. Examples: Cyclopentasiloxane, dimethicone.
Film-Forming Agents – 10%
These ingredients create a protective film on the skin’s surface, helping the product adhere better and remain effective for longer periods, especially when exposed to water or sweat.
Examples: PVP (polyvinylpyrrolidone).
Additional Ingredients (up to 6% w/w)
These ingredients offer additional skin benefits. Examples: Jojoba oil, avocado oil, hyaluronic acid.
Parfum – 3%
Added fragrance to give the sunscreen a pleasant scent.
Colourants – 2%
Colourants give the product a specific hue, though minimal amounts are used in sunscreen oils to avoid leaving a visible tint on the skin. Examples: Iron oxides, yellow 6, red 28.
Thickeners – 1%
These are used to adjust the viscosity and texture of the formulation, ensuring the product is easy to apply and spreads evenly without being too runny. Examples: long-chained fatty alcohols.
Preservatives, Antimicrobials – 1%
Preservatives prevent microbial growth, ensuring the product remains safe and stable during use. Examples: Phenoxyethanol, parabens.
Oils – To 100%
Oils provide hydration and skin conditioning, giving the product its characteristic oil-based texture and helping it spread smoothly across the skin. Examples: Vegetable oils (e.g., sunflower oil, coconut oil), mineral oil.
Sunscreen Hydrogel
Ingredient | Maximum concentration (% w/w) |
Ethanol (alcohol, alcohol denat.) | 60 |
UV filters | 25 |
Humectants | 10 |
Additional ingredients | 6 |
Silicones(including volatile silicones) | 5 |
Emulsifying agents | 5 |
Polymers | 5 |
Colourants | 2 |
Parfum | 1 |
Preservatives, antimicrobials | 1 |
Aqua | to 100 |
Ingredient Types and functions in sunscreen hydrogels
Ethanol – 60%
Ethanol acts as a solvent and provides a lightweight feel. It helps the product dry quickly and aids in delivering active ingredients. Examples: Alcohol denat.
UV Filters – 25%
UV filters protect the skin by absorbing or reflecting harmful ultraviolet (UV) rays, providing broad-spectrum sun protection. Examples: Octinoxate, avobenzone, octocrylene.
Humectants – 10%
Humectants help to draw moisture into the skin, preventing dehydration and keeping the skin hydrated. Examples: Sorbitol, glycerin.
Additional Ingredients – 6%
These ingredients are included for additional skin benefits, such as soothing or antioxidant properties. Examples: Plant extracts (like aloe vera), vitamins (like vitamin E, vitamin C).
Silicones – 5%
Silicones give the product a smooth feel, improve spreadability, and provide a light, non-greasy finish. Examples: Cyclopentasiloxane, dimethicone.
Emulsifying Agents – 5%
Emulsifiers help blend the oil and water components of the formulation, ensuring a stable, uniform product. Examples: Cetearyl palmitate.
Polymers – 5%
Polymers are used to create the gel-like texture and provide stability to the formulation. Examples: Carbomer.
Colourants – 2%
Colourants are added to give the product a specific tint or appearance, though only in small amounts to avoid leaving visible residue on the skin.
Parfum – 1%
Fragrance is added to provide a pleasant scent to the product.
Preservatives, Antimicrobials – 1%
Preservatives ensure the product remains free from microbial contamination and extends its shelf life. Examples: Phenoxyethanol, parabens.
Aqua – To 100%
Water acts as the main solvent, providing the base for the hydrogel formulation.
Sunscreen Gel (Oil Based)
Ingredient | Maximum concentration (% w/w) |
Silicones(including volatile silicones) | 40 |
UV filters | 25 |
Film forming polymers | 10 |
Thickeners | 10 |
Additional ingredients | 6 |
Colourants | 2 |
Preservatives, antimicrobials | 2 |
Parfum | 1 |
Antioxidants | 0.5 |
Oils | to 100 |
Ingredient Types and functions in sunscreen gels (oil based)
Silicones – 40%
Silicones improve spreadability, provide a silky feel, and help create a barrier on the skin. Volatile silicones evaporate quickly, leaving a non-greasy finish. Examples**: Cyclopentasiloxane, dimethicone.
UV Filters – 25%
UV filters protect the skin by absorbing or reflecting harmful UV rays, providing sun protection. Examples: Octocrylene, avobenzone.
Film Forming Polymers – 10%
These create a thin, protective film on the skin, improving product longevity and water resistance. Examples: PVP (Polyvinylpyrrolidone).
Thickeners (up to 10% w/w)
Thickeners give the gel its consistency and prevent separation of ingredients. Examples: Xanthan gum.
Additional Ingredients – 6%
These can include plant extracts or vitamins that provide added skin benefits, such as soothing or antioxidant properties. Examples: Aloe vera extract, vitamin E, glycerin, coconut extracts.
Colourants – 2%
Colourants give the product a specific colour, though typically used in small amounts to avoid visible residue. Examples: Iron oxides, titanium dioxide.
Preservatives, Antimicrobials – 2%
These ingredients ensure the product remains free from microbial contamination and has a longer shelf life. Examples: Phenoxyethanol, parabens.
Parfum – 1%
Fragrance is added to give the product a pleasant scent.
Antioxidants – 0.5%
Antioxidants help protect the skin from free radicals and oxidative damage. Examples: Vitamin E (tocopherol), green tea extract.
Oils – To 100%
Oils act as emollients, providing moisture and enhancing the spreadability of the product, act as the main phase in oil based gels. Examples: Vegetable oils (such as sunflower oil), mineral oil.
Sunscreen Stick
Ingredient | Maximum concentration (% w/w) |
Waxes, fats | 60 |
UV filters | 35 |
Bulking agents | 20 |
Emollients | 15 |
Silicones(including volatile silicones) | 10 |
Additional ingredients | 6 |
Colourants | 2 |
Antioxidants | 1 |
Oils | to 100 |
Ingredient Types and functions in sunscreen sticks
Waxes, Fats – 60%
Waxes and fats provide the solid structure and texture of the stick, making it easy to apply and allowing it to glide smoothly over the skin. Examples**: Theobroma cacao seed butter (cocoa butter), polyethylene.
UV Filters – 35%
UV filters protect the skin from harmful UV radiation by either absorbing or reflecting the rays. Examples: Zinc oxide, octocrylene.
Bulking Agents – 20%
These ingredients increase the volume of the formulation without impacting its performance. They help improve texture and consistency. Examples: Kaolin, nylon powder.
Emollients – 15%
Emollients soften and smooth the skin, enhancing the spreadability of the product while providing a moisturising effect. Examples: Cetearyl octanoate.
Silicones – 10%
Silicones improve the product’s texture and spreadability, providing a silky feel on the skin. Volatile silicones evaporate, leaving a lightweight finish. Examples: Cyclopentasiloxane, dimethicone.
Additional Ingredients – 6%
These include skin-soothing or protective agents that provide added benefits. Examples: caffeine, niacinamide, plant extracts.
Colourants – 2%
Colourants provide the desired colour to the product. Examples: Titanium dioxide, iron oxides, yellow 10.
Antioxidants – 1%
Antioxidants protect the skin from oxidative stress and help maintain the product’s stability. Examples: Vitamin E (tocopheryl acetate).
Oils – To 100%
Oils act as emollients and help enhance the spreadability of the product. Examples: Vegetable oil, mineral oil.
Regulation of Sunscreen Products
United States (FDA Monograph)
In the USA, sunscreens are regulated as over-the-counter (OTC) drugs by the U.S. Food and Drug Administration (FDA) under the Monograph system (21 CFR Part 352). As OTC drugs, sunscreens must adhere to strict drug regulations regarding safety, efficacy, and labelling.
Sunscreen products must comply with the ingredients, concentrations, and formulations outlined in the FDA’s final sunscreen monograph. Ingredients not included in the monograph must undergo the New Drug Application (NDA) process.
Sunscreens are treated as pharmaceutical products because their primary function is to mitigate or prevent a medical condition (i.e., sunburn, skin cancer).
European Union (Cosmetics Regulation EC No 1223/2009)
In contrast, sunscreens in the EU are classified as cosmetic products under the EU Cosmetic Regulation (EC No 1223/2009). The regulation governs product safety, permissible ingredients, and labelling requirements, with a focus on consumer safety rather than therapeutic efficacy.
Sunscreens must comply with Annex VI of the regulation, which lists allowed UV filters and their maximum concentrations. Sunscreens products in the EU must meet SPF and broad-spectrum protection requirements but are not classified as medicinal products unless they make therapeutic claims beyond UV protection.
UV Filter Ingredient Regulations
USA
The FDA regulates the specific UV filters permissible for use in sunscreen formulations through the OTC Monograph. Currently, only 16 active ingredients are recognized as safe and effective, including:
Organic (chemical) filters: Oxybenzone, Avobenzone, Octinoxate, Homosalate.
Inorganic (physical) filters: Titanium Dioxide, Zinc Oxide.
Recent developments have highlighted concerns over several chemical filters such as oxybenzone and octinoxate, prompting the FDA to request more safety data to determine if they meet the Generally Recognized as Safe and Effective (GRASE) standard.
EU
In contrast, the EU permits the use of 29 UV filters listed in Annex VI of the Cosmetic Regulation. This includes several filters not approved in the USA, such as Tinosorb M, Tinosorb S, and Mexoryl SX. The European regulatory framework allows broader flexibility in formulation, with both organic and inorganic filters playing a significant role.
The EU allows the use of titanium dioxide and zinc oxide in nano-form, provided they meet safety evaluations, a point of regulatory divergence from the USA, where nanoparticulate sunscreens face greater scrutiny.
Efficacy Testing and Labelling Requirements
USA
In the USA, sunscreens must undergo specific testing protocols outlined by the FDA to substantiate claims such as Sun Protection Factor (SPF), broad-spectrum protection, and water resistance.
Sunscreens are tested in vivo on human skin to determine their SPF, which measures UVB protection. Products must pass a critical wavelength test (greater than 370 nm) to claim protection from both UVA and UVB radiation. Products can claim either 40 or 80 minutes of water resistance, depending on validated testing.
EU
In the EU, efficacy claims such as SPF and UVA protection must comply with ISO standards:
SPF Determination (ISO 24444): SPF is tested in vivo, and sunscreens must offer a minimum SPF of 6 to be marketed.
UVA Determination (ISO 24443): Products must provide 1/3 of the SPF value as UVA protection and pass the UVA-PF test (ISO 24443).
Water Resistance Determination (ISO 16217 & ISO 18861): Water resistance claims are also tested according to ISO 16217 and ISO 18861, though only a 40-minute resistance is recognized in many formulations.
The EU also enforces the Colipa guidelines for labelling, which require sunscreens to display standardised information, such as “high protection” or “very high protection,” depending on the SPF.
Claims of Sunscreen Products
Permitted Claims in the USA for Sunscreen Products
In the USA, sunscreen labelling is strictly regulated under the FDA’s OTC Monograph rules.
Products must display the SPF value prominently. If they provide UVA protection, they can carry a “broad-spectrum” label. The SPF value of the products must be at least SPF 15 and a critical wavelength above 370 nm.
Sunscreen labels must indicate water resistance (40 or 80 minutes) or state that the product is “not water-resistant.” For water-resistant claims, third-party testing is required. During testing, sunscreen is applied to volunteers who are then submerged in water (25–32°C) up to the middle of their back, with gentle movement. After 20 minutes in water and 20 minutes of drying, the process is repeated until 40 minutes of total immersion is reached for a 40-minute claim. The SPF is measured afterward to confirm its effectiveness. For “very water-resistant” products, testing continues until 80 minutes of immersion. Non-water-resistant sunscreens must advise using water-resistant products when swimming or sweating.
Sunscreens cannot be labelled as “sunblock” or claim to offer “instant protection” or “protection for more than 2 hours without reapplication.”
Permitted Claims in the EU for Sunscreen Products
Products must list the SPF and use standardised descriptors such as “low,” “medium,” “high,” or “very high protection” according to the Colipa guidelines.
Broad-Spectrum Claims: A UVA logo must be displayed if the product meets the 1/3 UVA-PF requirement.
Water resistance claims must be substantiated, and misleading terms such as “waterproof” are prohibited. The European standard for water resistance testing was established in 2005. It includes two test durations: 40 minutes and 80 minutes, with a 15-minute drying period between each immersion. The water temperature is maintained at 29°C, with a tolerance of ±2°C. To make a water resistance claim, the SPF must remain at or above 50% of the initial value after immersion, with a 90% confidence interval.
Non-permitted Claims
Sunblock/Total Sun Protection
Sunscreen products help protect against UV radiation, but no sunscreen product is 100% effective. Leading consumers that the product will “block out the sun” or words to that effect, is misleading and cannot be substantiated. The claim “total sun protection” falls into the same category as a sunscreen product cannot guarantee sun protection to all radiation all the time, especially considering rubbing, towelling and swimming.
Lasts All Day
Unlike colour cosmetic claims where you can claim “lasts all day” mainly on consumer perception studies, “lasts all day” has a different meaning for sunscreen products as it insinuates an efficacy claim, for which consumer perception studies cannot be used. Sunscreen products should be reapplied consistently to maintain the SPF value on the bottle, a singular application of any SPF value does not guarantee protection for the whole day.
Reef Safe
“Eco-friendly” claims have gained popularity as of late, and the effects sunscreen actives have on coral reefs have raised some concerns. The studies are however preliminary, which doesn’t stop the eco-warriors from spreading misinformation about sunscreens and coral reefs. Yes, we should protect our coral reefs, but we need to further our knowledge in this field rather than putting sunscreen into a 1 m² tank with some coral extracts. “Reef safe” cannot be substantiated due to the lack of ‘real world’ or representative tests which can be carried out, furthermore, it denigrates other sunscreen products on the market, making them appear as if other products are not safe for coral reefs. Studies show that mineral sunscreen products are less/not harmful to coral reefs, so there is a general market trend to move toward mineral and away from chemical sunscreen products.
