Sun Protection Factor (SPF) isn’t just an essential element of skincare regime, but rather it forms an integral part of the dermatological advice for maintaining healthy skin. The British Association of Dermatologists frequently emphasises wearing sun protection throughout the year, to safeguard skin from the deleterious effects of the sun’s ultraviolet radiation. Heck, I bang on about it all the time (as a milky-white redhead, I have first-hand experience of what happens when you do not heed these warnings). In this blog post, I aim to delve into the medicinal and practical intricacies of SPF, decoding the differences between physical (also known as mineral) and chemical sunscreens, and exploring the reasons for promoting regular SPF use.
UVA = AGING, UVB = BURNINGTo begin with, let’s understand the importance of SPF usage. The sun emits ultraviolet radiation in the form of UVA and UVB rays. While UVA rays penetrate deep into the dermis, the skin’s thickest layer, causing premature skin ageing and photo-ageing, UVB rays burn the superficial layers leading to sunburn and playing a key role in skin cancer development. SPF acts as a crucial shield against these harmful ultraviolet rays, preventing them from damaging the skin.
SPF is described as the measure of a sunscreen’s ability to prevent UVB radiation from harming the skin. If used correctly, a sunscreen with SPF 30 provides approximately 97% protection from UVB rays. The Association, while imparting guidance on SPF usage, outlines the necessity to opt for a broad-spectrum product, which offers coverage against both UVA and UVB rays.
SPFs are typically categorised into two types based on their mechanism of operation – Physical SPF and Chemical SPF. Both have distinct compositions, and their work methodologies differ, leading to varied protective outcomes.
1. Physical Sunscreens: Akin to a physical shield, these sunscreens work by deflecting or blocking UV radiations. They contain active mineral ingredients, predominantly zinc oxide or titanium dioxide, which act as natural broad-spectrum agents shielding against both UVA and UVB rays. They commence their work the moment you rub them on your skin and are less likely to cause skin irritation, making them ideal for sensitive or rosacea-prone skin and infants.
2. Chemical Sunscreens: As the name suggests, chemical sunscreens use chemical compounds like oxybenzone, octinoxate, avobenzone and more to absorb the UV radiation. After absorbing, they convert it into heat and release it from the skin. This preventive mechanism operates against individual UVA and UVB rays and often requires a combination of chemicals to achieve broad-spectrum protection. Although less visible on the skin than physical sunscreens, they might require more reapplication and could cause skin irritation or allergic reactions.
An essential guideline from the British Association of Dermatologists is that while choosing a sunscreen, in addition to considering the SPF rating, it is advisable for persons with sensitive skin types to opt for physical sunscreens while others may choose chemical ones. However, for all skin types, a broad-spectrum sunscreen, water and sweat resistant property and an SPF of at least 30 is recommended.
Deciphering the Math Behind SPF Calculation and Its Implication
The numerical factor affixed to SPF, often seen on sunscreen products, reflects the measure of UVB protection it offers. The calculation of this SPF count is rooted in a comparison of the amount of sun exposure required to cause sunburn on unprotected skin versus the amount required to cause sunburn on protected skin.
Simply, if a person who would generally start to burn after 10 minutes in the sun uses an SPF 30 sunscreen, theoretically, they could stay in the sun 30 times longer (approximately 5 hours) without getting sunburnt. However, this is estimated under laboratory conditions, and real-life experiences may vary due to multiple factors such as the intensity of sunlight, application method, personal skin type, and sweating or water exposure.
The SPF number does not indicate overall protection but specifically highlights the extent of UVB protection – the rays primarily responsible for sunburn and skin cancer. An SPF 15 sunscreen blocks about 93% of UVB radiation, while SPF 30 blocks 97%, and an SPF 50 blocks about 98%.
What does SPF mean anyway?
One mistaken belief generally held about SPF ratings is that a sunscreen with double the SPF provides double the protection, which is not accurate. Moving from SPF 30 to SPF 50 only gives a 1% improvement in UVB protection. While higher SPF numbers do offer more protection, the degree of this increment diminishes as the SPF number rises.
No sunscreen can block 100% of UV rays and so allow me to reiterate the importance of broad-spectrum sunscreens that offer protection against UVA rays as well. UVA rays cause premature ageing and are also implicated in skin cancer. Remebmer no matter how high the SPF, sunscreen needs to be reapplied every two hours or immediately after swimming, heavy perspiration or towel drying. The British Association of Dermatologists advises using about six to eight teaspoons of sunscreen to cover the entire body and a teaspoon for the face and neck.
The SPF numerical factor is a handy gauge for consumers to comprehend the level of UVB protection a sunscreen affords, but it should not be the sole deciding factor. The selection of sunscreen should also consider its broad-spectrum cover, water resistance, formulation (physical or chemical), and, importantly, the individual’s skin type and sun exposure. Ultimately, conscious and regular sunscreen application, along with other protective practices, can serve as an effective sun defence strategy.
This post must underline that while SPF plays a vital role in prohibiting skin damage and skin cancer, it is not wholly foolproof. Therefore, don’t completely rely on it, and complement its use with other sun-protection habits such as donning hats, sunglasses, and sun-protective clothing, seeking shade, and dodging the sun during peak hours – the old Aussie ‘SLIP, SLAP, SLOP’!
In summary, understanding and implementing the regular usage of the appropriate SPF, aligned with your skin type and sun exposure, is fundamental for shielding your skin from the harms of UV radiation. Following the British Association of Dermatologists guidelines and consulting with a dermatologist for personalised advice on SPF usage can further enhance the skin’s health and longevity. SPF is not just skincare, it is indeed skin health care.
Remember, the sun doesn’t discriminate among its radiation recipients. Irrespective of age, skin type, or geographical location: SPF is for everybody!
Sources:- British Association of Dermatologists (www.bad.org.uk)- American Academy of Dermatology Association (www.aad.org)
