Sunscreen

Introduction

The sun's ultraviolet (UV) radiation is invisible to humans yet it is the main cause of skin cancer.

Within the UV spectrum, it can be subdivided into 3 types:

UVA

Leads to tanning and photo ageing & exacerbate the carcinogenic effects of UVB rays

UVB

Chief culprit of sunburn and plays a key role in developing skin cancer

Completely absorbed by the earth's atmosphere.

The 5S

To minimize solar damage to the skin

Slip on clothing that covers as much skin as possible
Slop on sunscreen
Slap on a broad-brimmed hat
Seek shade
Slide on sunglasses

NOTE: The degree of photoprotection provided by clothes is defined by the ultraviolet protection factor (UPF), which indicates how effective a fabric is at blocking out solar ultraviolet radiation. Yarn composition, tightness of the weave, and dark colours increase a garment's UPF.

Why use Sunscreen?

When used as directed, sunscreen is proven to:

Decrease your risk of skin cancers and skin precancers.

Regular daily use of SPF15 sunscreen can reduce risk of developing squamous cell carcinoma (SCC) by about 40% and lower melanoma risk by 50%.

Help prevent premature skin aging caused by the sun, including wrinkles, sagging and age spots.

How Does Sunscreen Work?

Sunscreen includes active ingredients that help prevent the sun's UV radiation from reaching the skin.

Chemical ingredients (such as avobenzone and octisalate) that absorb UV radiation.
Physical ingredients (such zinc oxide and titanium dioxide) that block and scatter UV radiation.

Many sunscreens available today combine both type of ingredients.

Who Should Use Sunscreen?

All individuals, regardless of skin phototype are subject to the potential adverse effects of ultraviolet (UV) radiation and will benefit from sunscreen use.

However, sunscreens are especially useful for individuals with light skin (phototypes I, II, and III) who are more susceptible to the acute (sunburn) and chronic (photoaging, skin cancer) adverse effects of excessive sun exposure.

Babies under 6 months old are the only exceptions as their skin is highly sensitive.

Choosing Sunscreen

With so many choices, make sure the sunscreen you choose is at least SPF30, broad-spectrum and water resistant.

Australian Cancer Council does not recommend aerosol sunscreen as it is very difficult to obtain the required amount of sunscreen necessary to get good UV protection.

Price is no indication of quality.

Sun Protection Factor (SPF)

Sun Protection Factor (SPF) is a laboratory-derived indicating a sunscreen's ability to block UVB from the skin.

The SPF number tells you how long the sun’s UV radiation would take to redden your skin when using the product exactly as directed versus the amount of time without any sunscreen.
So ideally, with SPF 30 it would take you 30 times longer to burn than if you weren’t wearing sunscreen.

When used as directed,

SPF 15 sunscreen filter 93.3% of UVB, allows about 6.7% UVB reaching the skin.
SPF 30 sunscreen filters 96.7% of UVB, allows about 3.3% UVB reaching the skin
SPF 50 sunscreen filters 98% UVB, allows about 2% UVB reaching the skin.

That may seem like a small difference until you realize that the SPF 30 is allowing 50% more UV radiation onto the skin compared to SPF 50.

NOTE: The testing does not compensate for reality factors such as wind, humidity, sweating, rubbing, water immersion or sensitized skin.

PA Rating System

The PA rating system (Protection Grade of UVA) was established in Japan, and is meant to inform users of the level of protection from UVA rays.

The PA rating system correlate directly with Persistent Pigment Darkening (PPD) method, which refers to how long it takes for the skin to tan.

In theory, a sunscreen with a PPD rating of 2, then it takes twice as long for your skin to tan when protected versus how long it would take while unprotected.

The correlations are as follow

PA+ (some UVA protection) = PPD between 2 and 4
PA++ (moderate UVA protection) = PPD between 4 and 8
PA+++ (high UVA protection) = PPD between 8 and 16
PA++++ (extremely high UVA protection) = PPD of 16 or higher

NOTE: Not all countries utilize PA rating system and some only recognize PA+++ as the highest protection available.

Broad spectrum

"Broad-spectrum sunscreen" means it protects against both UVA and UVB radiation.

The PA rating system is not commonly used in European countries and the US.

To pass the FDA's broad-spectrum test, sunscreens must provide

UVA protection proportional to their UVB protection.
Higher levels of UVA and UVB protection with higher levels of SPF.

Water Resistant and Very Water Resistant

No sunscreen is waterproof; they all eventually wash off.

Sunscreens labelled water resistant are tested to be effective for up to 40 minutes of swimming
Very water resistant sunscreens stay effective for up to 80 minutes in the water

Applying Sunscreen

Most people don’t apply enough sunscreen, which is why undesirable sunburns and tanning can occur despite sunscreen application.

To achieve the Sun Protection Factor reflected on a bottle of sunscreen, you should use approximately 2 mg of sunscreen per cm² of skin.
In practice, this means applying the equivalent of a shot glass (2 tablespoons) of sunscreen to the exposed areas of the face and body - a nickel-sized dollop to the face alone. If you’re using a spray, apply until an even sheen appears on the skin.

You should apply liberally to all exposed areas 20-30 minutes before sun exposure and regardless of the SPF used, it is still very important to reapply it regularly (e.g. every two hours or immediately after swimming or sweating).

Sunscreen can be easily wiped, loss through perspiration and is often applied unevenly.
Do not assume that doubling the SPF equal to doubling the safe exposure time.

When it is cold or cloudy, many choose to spend all day outdoors with no protection from the sun and in the end having some extent of sunburns.

Contrary to popular belief, up to 40 % of the sun's ultraviolet radiation still reaches the earth on a completely cloudy day. So, apply your sunscreen please.

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