During the testing, manufacturers apply 2 mg/cm2 of the sunscreen to the skin but in real life people usually apply much less, only around a quarter to half of this amount (0.5 – 1 mg/cm2) and reduce the protection indicated by the labelled SPF. Therefore, a sunscreen with a high SPF such as 50 will only give an SPF of between 3 and 19.
To meet the government recommendation, an adult would need to use 35ml of sunscreen (SPF15) per application. If reapplied every two hours, as is also recommended, a standard 200ml bottle would be used up in two to three days. This is impractical and expensive.
Sunscreens carry the ‘Boots star rating system’, which indicates the ratio of UVA and UVB protection. As discussed in a previous blog, the SPF refers to the amount of UVB protection offered and the stars indicate UVA protection; more stars, more UVA protection. UVA makes up more than 95 per cent of UV radiation and contributes to ageing, UVB is the main cause of sunburn. A 5-star product at a lower SPF (SPF 15) could provide less protection than a 3-star product at a higher SPF (SPF 30), so apply higher factors to all unprotected areas. Spread sunscreen evenly rather than rub it in and re-apply regularly.
Sun is the dominant factor in the onset of premature ageing! Had we always protected our faces, the way Japanese women often do, our skin would age in a different, subtle way.
Ageing with sun protection
Our aged face would have a smooth and even surface with only few fine wrinkles. We would be able to distinquish some loss of elasticity (due to thickenned, disoriented bundles) and thinning (atrophy) but no signs of inflammation and only a moderate decrease in perfusion giving our facial skin slightly drawn, pale appearance. The upper skin layer, epidermis, would be still working well in comparison to photo-aged skin.
Ageing in the sun (photo-ageing)
If we have suntanned all our life, our facial skin will have an uneven (bumpy) surface and sallow, yellowish tone with mottled pigmentation (sun spots). We will see coarse wrinkles and a severe loss of elasticity (due to the thickening of dermis and increase in elastotic amorphous mass, less structural fibres and underlying inflammation). Also the capillaries become prominent on the skin surface (teleangiectasia) contributing to the uneven skin colour. Epidermal changes – and the risk of skin cancer – are also profound.
Topically applied sunscreens protect by absorbing or reflecting radiation at the skin surface. UV filters can be grouped into two broad categories: organic (previously called chemical) and inorganic (previously called physical) (Yaar and Gilchrest, 2007). Organic sunscreens absorb UVR, convert it into heat, and thus prevent photons from interacting with molecules in the skin. Organic sunscreens are usually „invisible‟ and hence cosmetically appealing.
Sun Protection Factor (SPF) of a sunscreen is primarily a measure of protection against UVB. It is defined as the minimal perceptible erythema, or minimal erythema dose (MED) ratio between sunscreen-protected and unprotected skin. If a person normally experiences the onset of redness to unprotected skin after 10 minutes of sun exposure, sunscreen with SPF 8 would provide protection against perceptible sunburn for 80 minutes. SPFs are now also categorised as providing low to very high protection: Low protection SPF 6 to 14/Medium protection SPF 15 to 29/High protection SPF 30 to 50/Very high protection SPF 50 + (i.e. SPF 50+).
It is recommended that people select sunscreens with SPF 30 or higher (Palm and O‟Donoghue, 2007) because they generally do not apply sufficient quantities of the product. The recommended SPF 30 takes into account these behavioural factors that lead to a reduced level of protection (if applied adequately, then SPF 15 is sufficient).
Sunscreens that offer both UVA and UVB protection are called „broad spectrum‟. The ‘star system’ indicates a product’s UVA protection, i.e.the % of UVA radiation absorbed by the sunscreen in comparison to UVB or the ratio between the level of protection afforded by the UVB protection and the UVA protection. Five stars indicates excellent protection against UVA equal to the SPF against burning, whereas one or more stars implies UVA protection equal to one or more fifths of the SPF against burning (Wahie et al., 2007). If choosing a low SPF, it may have a high level of stars, not because it is providing high UVA protection, but because the ratio between the UVA and UVB protection is about the same. That is why it is important to use a high SPF in conjunction with high UVA protection!
The Sunscreen Rules
- The overall message in terms of sunscreen use is – more is better.
- Choose a sunscreen labelled „photostable, broad spectrum‟ which offers both UVA and UVB protection.
- Use a „high protection‟ sunscreen of at least SPF 30 to protect against UVB and high UVA protection - at least 4 stars and the circular UVA logo.
- Apply half an hour before going out in the sun, and half an hour after commencing sun exposure to prevent an additional 65 to 80 percent of UV light (Lowe, 1990) and corrects missed patches of skin. Don’t forget your the other exposed areas – head, neck and ears (Fry and Verne, 2003).
- Reapply sunscreen at least every two hours, and immediately after contact with water, even if the sunscreen is „water resistant‟, and also after towel drying.
- Apply sunscreen liberally. Adults should apply an equivalent to a full shot glass (~35 ml) evenly on the whole body (Wulf et al., 1997) and rub it in after application in order to avoid skip areas (Neale et al. 2002, Barr 2005).
- Aftercare is also important. Apply aftersun products to moisturise your skin after sun exposure.
Preventing skin cancer
The role of photoprotection products against malignant melanoma is complex. A systematic review in 2003 failed to show that sunscreen use had any preventive effect (Dennis et al., 2003). However, used appropriately, sunscreens have been shown to be extremely efficient against burning, DNA damage and immunosuppression of the skin. Regular and careful use of sunscreens has been clearly shown to reduce the incidence of actinic keratoses and squamous cell carcinomas but not necessarily basal cell carcinomas (Darlington et al., 2003; Green et al., 1999).
The tanned face is attractive but over-exposure to the UV light is damaging to the skin cell’s DNA and causes sunburn (in severe cases also blistering and pain). Take care and prevent skin cancer (melanoma), now the most common cancer amongst women in their 20s!
Stay Safe in the Sun
- Avoid the sun during the hottest part of the day, between 11am and 3pm. Find shade under umbrellas, trees or other shelters.
- Always cover up, sunscreen alone is not enough. Wear T-shirts, wide-brimmed hats and UV protective sunglasses.
- Apply sunscreen generously, also when travelling as sun will still have an effect on your skin through the windows.
- Use sunscreen with UVB protection of at least SPF 30 (SPF 50 for children and people with pale skin) and also high UVA protection.
- Keep babies and young children out of direct sunlight!
If concerned about changes in your skin following sun exposure – particular attention should be paid to moles that change in shape, size or colour – consult a local specialist. FaceWorkshops have teamed up with a Consultant Dermatologist, Dr James Britton, at Spire Hull and East Riding Hospital. You can see him privately or your GP can refer you via the NHS, please call for his contact details.