Sunglass at the poolside

What is SPF? Why is it important?

SPF stands for Sun Protection Factor. It measures the level of protection a sunscreen or a piece of sun protective clothing has against UVB rays. Protect yourself from the harmful effects of the sun. Understand the amount of protection you are receiving from SPF products.

Ultraviolet (UV) Radiation

Sunshine is made up of different rays. Ultraviolet (UV) radiation is the part of sunlight which causes sunburn, skin damage, and skin cancer. Ultraviolet radiation can be broken down into three bands: UVA, UVB, and UVC.

UVA Rays
Ultraviolet A rays are the cause of long term skin damage & photo-aging. They cause premature ageing, wrinkles, and sun spots. Associating the 'A' in UVA with Ageing is a good way to remember its harmful effects, UVAgeing.

On top of damaging your skin, UVA rays can make you sick too. Exposure to UVA rays can suppress the immune system. It increases the risk of viral, bacterial, parasitic, or fungal infections.  It may reduce the effectiveness of vaccines.

UVB Rays
Ultraviolet B rays are the cause of sunburn. They usually burn the superficial layers of your skin known as the epidermal layers.

They are also the common cause of most skin cancers. The intensity of UVB rays vary by season, location, and time. It is the strongest between 10am and 4pm. You can associate the 'B' in UVB as UVBurning.

UVC Rays
Ultraviolet C rays are the strongest and most deadly of solar rays. Fortunately, the ozone layer protects us from them. It is therefore imperative for the survival of humans not to damage the ozone layer.

What Does the SPF Value Mean?

The SPF value is about duration, not strength. It determines the length of time before your skin gets sunburned. This will vary depending on your skin type. A person with fair or sensitive skin will burn up much faster than a person with normal skin.

To calculate the duration of the sunscreen protection, you will need two values:

  • SPF value of your product
  • Time it takes your skin to burn

Let's say you start getting sunburned after 10 minutes in the sun without any sunscreen. Applying a sunscreen with SPF 30 would protect you for 10 minutes x SPF 30 = 300 minutes before you begin to burn. That means a protection against UVB rays of up to 5 hours.

SPF Number x Time to Burn = Time to burn with protection

However, do note that when evaluating SPFs, testers apply two milligrams of sunscreen per square centimetre of skin. Most people apply from only 0.5 to one milligram per square centimetre of skin in their everyday life. The protection they are receiving from the SPF is approximately 1/3 of the labelled value.

That would bring the effective duration of protection we calculated above from 300 minutes to only 100 minutes. You are most likely not applying enough sunscreen.

On top of that, the weather, amount of sweating, swimming, drying yourself, and skin types will also affect your level of protection. You should reapply sunscreen every two hours regardless of its SPF factor.

Different Levels of SPF

No sunscreen can block all UVB rays. However, in terms of percentages, a sunscreen with SPF 15 will filter out approximately 93% of the UVB rays you are exposed to, one with SPF 30 keeps out about 97% and an SPF 50 sunscreen block 98%.

Sun Protection Factor (SPF)Protection Against UVB Rays
SPF 250%
SPF 475%
SPF 1090%
SPF 1593%
SPF 3097%
SPF 5098%
SPF 7098.5%
SPF 10099%

The Higher the SPF Value the Better?

As you can see from the table above, sunscreens with really high SPFs, such as SPF 70 or SPF 100, do not offer significantly greater protection than SPF 30. People are often misled into thinking they have more protection than they actually do.

Products with very high SPFs may also encourage individuals to neglect other photoprotective behaviours, like seeking the shade and wearing sun-protective clothing.  By preventing sunburn, sunscreens with very high SPFs can create a false sense of security, prompting consumers to stay out in the sun longer.  Sun damage (for example, UVA damage) can take place without skin-reddening doses of UV radiation, and even the best sunscreens should be considered just one vital part of a comprehensive sun protection regimen. To avoid such a scenario, many health regulatory bodies around the world have capped the SPF of sunscreens at 50+.

The importance of using both UVB and UVA protection cannot be emphasized enough. It is recommended to use products between SPF 30 and SPF 50. In addition to SPF 30+, your sunscreen should include some combination of the following UVA-blocking ingredients:

  • zinc oxide
  • titanium dioxide
  • avobenzone
  • ecamsule
  • oxybenzone

Sunscreens with both UVA and UVB protection may be labelled as:

  • multi spectrum
  • broad spectrum
  • UVA/UVB protection

Additionally, in order to have broad spectrum protection, the UVA protection should be at least 1/3 of the UVB protection. High SPF sunscreens usually offer far greater UVB than UVA protection, thus offering a false sense of full protection. Individuals applying high-SPF sunscreens may not burn, but without UVA-screening ingredients they can still receive large amounts of skin-damaging radiation.

Leave a Reply