THE BASE OF SKINCARE: SUN PROTECTION
Sunscreens are considered in the European Union to be cosmetics that play an active role in preventing oncological problems, particularly skin cancers.
The name sunscreen tells us that it protects us from the sun, but the truth is that sunscreens protect us from one part of the sun, namely ultraviolet (UV) radiation. Unlike visible light, which, as the name suggests, we can see, and infrared radiation (IR), which produces heat and we can feel, UV radiation cannot be seen or felt. It is usually related to IR radiation, but not always. In other words, the hottest days are not necessarily those with the most UV radiation, although this is the rule most of the time. So it's important to realise that even in cloudy or rainy weather, the sun continues to emit UV radiation.
Exposure to UV radiation (radiation that passes through windows - even car windows - and most clothing - unless it has UV protection) promotes the mutation of skin cells that can result in skin cancers. In addition to this obvious need for protection, daily use of sunscreen also prevents premature skin ageing and the worsening of pathologies such as melasma, rosacea and acne. It is known that UV radiation is responsible for the majority of ageing caused by external factors (the percentage is debated, but it is somewhere between 70-80%), thus reinforcing the importance of daily sun protection.
At AVENUE CLINIC, we believe prevention is the base for healthy skin.
WHICH SUNSCREEN TO CHOOSE?
The World Health Organisation recommends a sunscreen with an SPF (Sun Protection Factor) of 15 or higher; most dermatologists recommend SPF30 or higher. If you're concerned about premature ageing and hyperpigmentation, we don't recommend less than SPF50+ in direct sunlight.
Another feature of sunscreen is that it's not eternal. When you inadvertently touch your face throughout the day, the sunscreen gradually comes off and is removed, reducing the protective "mesh" created when you apply it. Sunscreen should therefore be renewed every 2 hours to ensure continued protection.
A common mistake in using sunscreen is using too little. SPF is calculated based on an application of 2mg/cm2 of skin, according to ISO 24444:2019. So a face protector of around 30 mL should last us for around a month of daily use and a body protector of 200 mL should only last 4-5 applications.
WHAT IS SPF?
The acronyms SPF (sun protection factor) or SPF (sun protection factor) appear on most sunscreen labels and, in Europe, have numbers that go up to 50+, the maximum protection that is declared on the label, so as not to mislead the consumer into thinking that a sunscreen can block 100 per cent of UV radiation. This number is a factor calculated by measuring the time it takes for skin exposed to UV radiation to scald. The difference between the level of protection of the highest SPFs would be almost negligible, if in fact everyone applied the amount of sunscreen used during the test conditions. As this doesn't happen in practice in most cases, the recommendation remains to use the highest protection factor available, in this case 50+.
This SPF measurement only refers to protection against UVB radiation, in addition we also have protection against UVA radiation and in this case the scales vary. In the EU it is compulsory for all sunscreens to have at least 1/3 of the UVB protection they have from UVA radiation, but for those who want high protection, we recommend looking for "high spectrum" sunscreens, or reading the label, looking for one of these symbols (image below), which vary depending on the market and country in which the sunscreen was marketed. Please consider the recent expansion of the Japanese PA scale to ++++, making it the maximum scale in this system.
In addition, no sunscreen protects 100% because there is no way to block 100% of UV radiation. That's why it's so important to add preventive behaviours to sun protection, such as avoiding sun exposure during peak radiation hours, wearing a hat and radiation-protective clothing, and wearing sunglasses, among others.
WHAT ARE SUN FILTERS?
Sunscreens have added ingredients called sun filters, which have been proven to protect against UV radiation, namely UVA and UVB radiation (UVC radiation is blocked by the ozone layer). For a long time it was believed that UVA radiation was responsible for premature skin ageing and UVB for cancer problems, but it is now known that both types of radiation are responsible for both issues.
Therefore, sun filters are combined in a sunscreen formulation to cover the majority of the UV spectrum and effectively protect the skin, thus forming the "broad spectrum" protection we were talking about earlier. There are mainly two types of sunscreen: chemical or organic and physical, mineral or inorganic. This classification of filters refers to their origin.
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Physical sunscreens are zinc oxide and titanium dioxide and are characterised by being very fine white powders. The first sunscreen formulations resembled an old-fashioned nappy rash ointment because they were white and thick. To get around this problem, these filters were micronised into smaller and smaller particles, until today we have sunscreens with these compounds that are practically transparent. These filters are still widely used in pediatric settings because they have a well-known safety profile, which some newer chemical filters do not (it is highly discouraged to do safety tests on cosmetics with babies and children).
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Chemical filters, on the other hand, are usually transparent and include molecules such as octocrylene, tinosorb S® (this is a brand name for the raw material, the name of the molecule is bemotrizinol), avobenzone, homosalate, among many others. Sunscreen formulations can include just one or two broad-spectrum sunscreens (which cover type A and B UV radiation), or they can come in a combination of several lower-spectrum filters which, when added together, cover the entire UV spectrum.
SUNSCREEN FOR VISIBLE LIGHT
In addition to the UV spectrum, there is more and more talk about the visible light spectrum (400-700 nm) and the infrared spectrum (>700 nm) and their impact on the skin and conditions such as melasma or rosacea. The truth is that there are currently no sunscreens on the market that protect across the entire spectrum of visible light. Visible light, unlike UV radiation, is not responsible for contributing to the risk of cancer because it doesn't cause DNA mutations, but it does contribute to oxidative stress, inflammation and melanogenesis (the process of synthesising melanin, the pigment that gives skin its colour) in people who are already prone to melasma and spots.
There is more and more evidence pointing to the need to add iron oxides to other sunscreens, as they enhance UV protection. These iron oxides are particularly important for those who suffer from spots and are pigments that are also found in make-up foundations and concealers.
The recommendation is therefore to use tinted sunscreens, which are actually the most practical and widespread. However, due to the limited variety of colours, they often influence the amount of sunscreen applied, making it less pleasant to use and leaving most people either too white or too dark. In these cases, sunscreen can simply be applied with a foundation of the appropriate colour, since all make-up foundations contain iron oxides that give them colour and zinc oxide and/or titanium dioxide as opacifiers. However, make-up should never be used as the primary source of sun protection because not enough is applied to provide protection, since applying 8-10g of foundation to the face and neck would be very difficult and would have a very unnatural result.
By Sara Fernandes, Masters in Pharmaceutical Sciences with a specialisation in Cosmetology, for AVENUE CLINIC