The resurgence of tanning trends on TikTok and other social media platforms raises significant concerns about the skin health of the Australian population, especially the youth. Australia’s ‘Slip, Slop, Slap, Seek, Slide’ campaign has long been at the forefront of sun safety education.1 However, recent viral challenges on social media such as the ‘tan line’ trend, where users deliberately create tan lines through sunbathing, promote unprotected sun exposure and downplay its well-documented risks. Given the widespread reach of social media, there is a pressing need for renewed public health messaging about evidence-based sun protection.
Effective sun protection involves key strategies used in combination: applying broad-spectrum, water-resistant sunscreen (SPF50+); wearing a broad-brimmed hat, sunglasses and sun protective clothing; and seeking shade when possible.2 Despite the importance of sunscreen, studies have shown that it is commonly insufficiently applied, contributing to inadequate sun protection.3–9 Clinicians are well positioned to educate patients on proper sunscreen use and holistic sun safety. A cross-sectional study, however, suggested that consumers do not receive guidance from dermatologists about sunscreen use and do not have adequate knowledge of current sunscreen guidelines.10 A large study in the United States revealed that sunscreen was mentioned in only 1.6% of all dermatology visits and 0.9% of all patient visits associated with skin disease.11 This highlights the need for improved patient education in all clinical settings.
Aim
This review aims to equip clinicians with a practical framework for patient education on comprehensive sun protection, with focus on the complexities of sunscreen use.
Benefits: Why do we recommend sunscreen use?
Sun exposure has well-documented dermatological consequences, including melanoma and non-melanoma skin cancers (NMSCs). Sun protection through regular sunscreen use has been shown to prevent these malignancies.12–14 Sun exposure also exacerbates pigmentary disorders, such as melasma, cutaneous porphyrias, cutaneous lupus erythematosus and polymorphic light eruption (PMLE).15–19 Lastly, sunscreen has been shown to prevent the photoageing effects of the sun, which can be a general concern for patients.20
Active ingredients: What makes sunscreen protective against the sun?
Sunscreens are largely divided into two groups, chemical/organic or mineral/inorganic, based on the type of UV filters that are used. In Australia, there are currently 27 chemical filters and two mineral filters that are approved by the Therapeutic Goods Administration (TGA) for use in sunscreens.21
Chemical sunscreens
Chemical sunscreens contain organic filters such as octocrylene, octinoxate, oxybenzone and avobenzone. These sunscreens protect the skin from UV radiation through the absorption of UV rays, which are then converted into heat and released from the skin.22 Chemical filters penetrate the stratum corneum and absorb specific wavelengths of UVA and UVB radiation, preventing them from causing cellular damage. As they need to be absorbed into the stratum corneum, these sunscreens should be applied 20 minutes prior to sun exposure (Table 1).
Mineral sunscreens
Mineral sunscreens, or physical sunscreens, contain the inorganic filters zinc oxide (ZnO) or titanium dioxide (TiO2). These filters act as a physical barrier against UV rays and provide protection by reflecting and scattering UV rays away from the skin. Mineral sunscreens have the benefit of causing less skin irritation, making them a preferred choice for individuals with sensitive skin or other skin conditions, such as rosacea and eczema.23 Traditional formulations contained larger particles of ZnO or TiO2, which leave a noticeable white appearance on skin. The development of micronised (100–2500 nm) and nanosized (1–100 nm) particles of these ZnO or TiO2 has allowed for more cosmetically acceptable mineral sunscreens.22 Safety concerns for nanoparticles is discussed later in this piece.
With a wide variety of sunscreen filters available, consumers are encouraged to choose a product that they find comfortable and are willing to use consistently. Table 1 outlines the key advantages and disadvantages of different sunscreen types to help guide selection.
| Table 1. Summary of some advantages and disadvantages of chemical/organic and mineral/inorganic sunscreens |
| Type |
Pros |
Cons |
| Chemical/organic sunscreen |
- Lightweight and easier to apply
- Cosmetically elegant with no white cast
- Formulas can be water-resistant
|
- Requires 20 minutes to absorb before sun exposure
- Can cause skin irritation or allergic reactions in sensitive individuals
- Some ingredients (eg oxybenzone, octinoxate) linked to environmental concerns, particularly coral reef damage
- Can degrade faster when exposed to sunlight, requiring frequent reapplication
|
| Mineral/inorganic sunscreen |
- Provides immediate protection after application
- Less likely to cause irritation, making it ideal for sensitive skin and children
- More photostable, offering longer-lasting protection
- Generally considered reef-safe and environmentally friendly
|
- Can leave a white appearance on skin, particularly on darker skin tones
- Thicker texture, which might feel heavy or greasy
- Might require more frequent reapplication because of potential rubbing or sweating off
|
Iron oxides
The addition of iron oxides to sunscreen can provide protection against visible light, which is implicated in pigmentary disorders and photodermatoses such as porphyria and cutaneous lupus erythematosus. Studies have demonstrated that iron oxide-containing sunscreens are superior in preventing visible light-induced pigmentation, particularly in individuals with skin of colour (SOC).24,25 Iron oxides provide tint to sunscreens and other cosmetic products. Patients with pigmentary disorders and photodermatoses, therefore, might benefit from the use of a tinted sunscreen in favour of a non-tinted sunscreen.
Sunscreen efficacy: How is the effectiveness of sunscreen determined?
The effectiveness of sunscreens is defined by several parameters. In Australia, the TGA issues a set of guidelines for the approval of sunscreens, which involves a set of rigorous testing to ensure its efficacy in sun protection.21 Products that receive TGA approval will receive a ‘AUST L’ identification number, which is displayed on the product packaging. However, Australian consumers now have easier access to international sunscreen products that might not have undergone TGA approval.
UVB protection
The sun protection factor (SPF) measures how much sunscreen increases the minimal erythema dose (MED) compared to unprotected skin. The MED is defined as the UVB dose required to produce minimal skin erythema.26 SPF is based on in vivo testing on human participants, with the sunscreen applied at a dose of 2 mg/cm2. Achieving the labelled SPF of a sunscreen, therefore, relies on application to this dose.
UVA protection
Broad-spectrum sunscreen provides protection against UVA radiation, which in Australia is indicated by a pass/fail test rather than a numerical grade.27 UVA protection of sunscreen is determined through in vitro testing of the critical wavelength of the sunscreen, which indicates the UV radiation that the product effectively blocks. A sunscreen product is labelled as ‘broad-spectrum’ by the TGA when it has both UVB protection, conveyed through its SPF rating, and passes the UVA test.21 In Europe, compliant sunscreens display a ‘UVA’ symbol enclosed within a circle on the packaging, which might also appear on some Australian products.
Recommendations: Ensuring adequate application and reapplication of sunscreen
The Cancer Council recommends using the five sun protection strategies when the UV index, which measures the UV radiation levels, is three or above.28 This following section elaborates on several key sunscreen recommendations to ensure adequate protection (Table 2).
It is recommended that Australians choose a broad-spectrum sunscreen with an SPF rating of 50 or 50+. An SPF rating of at least 50 means that at least 98% of the UVB radiation is being filtered by the sunscreen, whereas broad-spectrum indicates adequate UVA protection.
The efficacy of sunscreen relies on adequate application and reapplication. Real-world studies have demonstrated that consumers apply only one-fifth to half of the required amount of sunscreen.3–9 To improve application, practical tools such as the ‘teaspoon’ guide and ‘finger unit’ guide have been developed to ensure sunscreen application to achieve the recommended dose of 2 mg/cm2 (Table 3).29–31 Both guides have been developed based on the ‘rule of nines’ for body surface area. The ‘teaspoon’ guide refers to the application of one teaspoon worth of sunscreen to each specified body area.30,31 The ‘finger unit’ guide can offer a more practical solution as it does not require measuring instruments – rather, two ‘finger units’ refers to the amount of sunscreen squeezed along the length of the index and middle fingers, from the palmar crease to the fingertips.29
Timing of application is also important to ensure sunscreen efficacy. Chemical sunscreens should be applied at least 20 minutes before sun exposure to allow adequate absorption into the stratum corneum, where the filters absorb UV radiation. To maintain photoprotective efficacy, sunscreen should also be reapplied every two hours during sun exposure, and immediately after swimming, sweating or towel drying. For chemical sunscreens, reapplication is necessary because of degradation over time upon sun exposure. In contrast, mineral sunscreens, which form a protective barrier on the skin surface and reflect UV radiation, require reapplication as they can be physically removed through routine activities.
| Table 2. Summary of sunscreen application recommendations and rationale |
| Recommendation |
Reasoning |
- Use a comprehensive sun protection strategy, which includes sunscreen, when the UV Index is 3 or above
|
- The UV Index indicates the level of UV radiation at ground level on a given day, with 1 being the lowest and 11 being extreme.28 A UV Index of 3 indicates moderate UV radiation exposure, which can cause damage to the skin
|
- Select a broad-spectrum sunscreen with an SPF rating 50 or 50+
|
- Higher SPF ratings provide better protection against UVB rays, which cause sunburn. Broad-spectrum sunscreens ensure UVA protection, which is responsible for skin cell damage
|
- Apply sunscreen 20 minutes prior to sun exposure
|
- This applies to chemical sunscreens, as the UV filters need to be absorbed into the stratum corneum, where they absorb UV rays
|
- Ensure adequate amounts of sunscreen are applied. Follow the ‘teaspoon’ rule for each body region as a guide (Table 3)
|
- The testing of sunscreen efficacy is based on application of sunscreen at a dose of 2 mg/cm2. Application of less sunscreen volume will result in inadequate sun protection30,31
|
- Reapply sunscreen every 2 hours or more frequently if swimming or sweating
|
- As mineral sunscreens sit on top of the skin and reflect UV rays, they can rub off over time because of physical activity or sweating
|
- Considering using a waterproof sunscreen if undertaking these activities
|
- Chemical sunscreens can degrade when exposed to sunlight, thus requiring reapplication. For example, the chemical filter, avobenzone, is photolabile and might lose 50% of its efficacy after 1 hour of UV exposure22,27
|
| Table 3. A recommendation on the amount of sunscreen applied to each body region for adequate coverage based on the ‘teaspoon’ and ‘finger units’ guides |
| Body region |
Number of teaspoons (5 mL) |
Finger unitsA |
| Face/head/neck |
1 |
2 |
| Right upper limb |
1 |
2 |
| Left upper limb |
1 |
2 |
| Anterior trunk |
1 |
4 |
| Posterior trunk |
1 |
4 |
| Right lower limb |
2 |
4 |
| Left lower limb |
2 |
4 |
| ATwo finger units refers to the amount of sunscreen squeezed along the length of the index and middle fingers, from the palmar crease to the fingertips. |
Common sunscreen issues: Concerns and how to address them
Texture, feeling and appearance
The sensory and aesthetic experience of applying sunscreen plays a crucial role in its uptake and compliance. Studies have found that the texture, feel and appearance of sunscreens can be a barrier to its use.32–34 A common complaint is the appearance of a white cast or greasy feeling on the skin after sunscreen application.34 This is often attributed to the large particle size of traditional mineral sunscreens, which sit on the skin surface and reflect light. Micronised or nanosized particles of ZnO or TiO2 are now increasingly used, offering a sheer and more cosmetically acceptable mineral sunscreen.22 In general, chemical filters also typically offer better cosmetic appearance and texture. Sunscreens are also available in many forms to suit consumer preference, including lotion, creams, gels, sprays, serums or integrated into makeup products, such as primers and powders. Overall, dermatologists agree that the best sunscreen is one that patients will comply with.35
Acne, rosacea and periorificial dermatitis
As mentioned, mineral sunscreens are generally better tolerated by patients with rosacea and eczema. However, conversely, the occlusive properties of traditional mineral sunscreens containing large particles of ZnO or TiO2 might trigger or flare skin conditions such as acne and periorificial dermatitis. In these patients, it might be beneficial to recommend newer micronized mineral filters or a switch to chemical filters. Patients with oily skin, acne or rosacea might also prefer lighter gel-based, serum or powder formulations.36
Contact allergy
Contact dermatitis results from a delayed hypersensitivity reaction to sunscreen ingredients. The most reported UV filters associated with contact allergy include oxybenzone (benzophenone-3), octocrylene and avobenzone.37 In addition to UV filters, sunscreen products often contain other potential allergens, such as fragrances, emulsifiers and preservatives, which can also trigger contact allergy. For patients with suspected contact allergy to sunscreen, a dermatology referral for patch testing can be recommended.
Environmental safety
Increasing awareness of the environmental impact of sunscreens, particularly concerning coral reef health, has led to growing consumer concern. Certain chemical filters, such as oxybenzone and octinoxate, have been implicated in coral bleaching and marine toxicity.38 However, real-world evidence for their direct impact on coral bleaching is limited and further research is required.
Safety of nanoparticles
Concerns regarding nanoparticle sunscreens have gained attention because of their potential for skin penetration and systemic absorption.39 Research to date indicates that nanoparticles of ZnO or TiO2 do not penetrate deeply enough into skin to reach viable epidermal layers.40 Although further research is required to ensure consumer safety, the current evidence supports the safety of nanoparticle sunscreens.
Conclusion
Sunscreen is an important component of photoprotection behaviours. Beyond its crucial role in prevention of skin cancers, it serves an important role in the management of other dermatological conditions, such as pigmentary disorders. Studies have shown that sunscreen remains underutilised or incorrectly applied by many individuals, resulting in inadequate sun protection.3–9 Education from healthcare professionals is lacking.11 This issue is compounded by social media trends promoting sun tanning, particularly among adolescents and young adults. This highlights the need for improved education through public health initiatives and from healthcare professionals, such as general practitioners, who are well-positioned to provide guidance on sun protection.
In addition to proper sunscreen usage, it is essential that other sun protection measures are also encouraged, such as wearing wide-brimmed hats, sunglasses, long-sleeve clothing and seeking shade.1 This review summarises key information to support clinicians in counselling patients on correct and effective sunscreen use. Given the complexities of sunscreen use, this review focuses on the properties, applications and common barriers to adherence. However, sunscreen is just one aspect of comprehensive sun protection. A holistic approach to sun safety remains essential and should be emphasised in patient education.
Key points
- Ultraviolet radiation is a key environmental risk factor for skin cancer, photoageing and pigmentary disorders.
- Comprehensive sun protection includes sunscreen, protective clothing, hats, sunglasses and shade-seeking behaviour.
- Sunscreen efficacy depends on proper application technique, amount and regular reapplication.
- Guidelines such as the ‘teaspoon rule’ or ‘finger-tip unit’ help standardise adequate sunscreen use.
- Clinicians play a vital role in addressing sunscreen misconceptions and promoting adherence through patient education.