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10th January 2011

SPF Explained

 

 

Sun care products are graded by the SPF rating system. This stands for Sun Protection Factor, and is usually expressed as a number between 2 and 35 (although SPFs as high as 50 are available).

The SPF number is an expression, in multiples, of your skin’s natural protection against the sun. The length of time it will fend off harmful rays is totally dependent on your sun-skin type and the number of minutes you can be exposed to the sun (without a sunscreen) before your skin starts burning. This is known as the Minimal Erythermal Dose, or MED.

Lets say you are a TYPE II and you burn within 10 minutes of exposure to the sun – an SPF4 cream will protect you from UVB rays for four times this number: 40 minutes; SPF10 will therefore allow you 100 minutes of protection, and an SPF25, 250 minutes.

However, the sun has an accumulative effect on the skin. This means that re-applying your SPF4 cream after 40 minutes, will not give you another 40 minutes of protection. You will need to cover up or go indoors.

The key to selecting an SPF product is being aware of the length of time your skin takes to burn in the sun, and the length of time you intend to stay out in it.
Your Sun Skin Type

Sun care products are essential ammunition in the fight against sunburn, premature aging, skin damage and skin cancer. However, choosing the most effective sun protection formula depends on knowing a number of key things about your skin.

Individual levels of natural sun protection vary enormously, and depend on the skin’s natural melanin content. People who are darker skinned have larger melanin cells and therefore greater natural protection against UV light. They require less additional sun protection compared to fairer skin types, who produce smaller melanin cells and are therefore at greater risk of sun damage.

  • TYPE I skin is very pale and naturally freckled. Hair is red or pale blonde and eyes are green or blue. This skin type burns easily in the sun, and goes bright red rather than a bronzed brown. It is associated with people of Celtic origin, and is seen most often in those of Irish or Scottish decent.
  • TYPE II skin is also pale. Hair can be blonde to light brown and eyes are blue or hazel. This skin type also burns easily but can go brown if sun exposure is introduced gradually. Common among people of Scandinavian or Germanic origin, it is also found in the UK.
  • TYPE III skin is normally quite pale, with dark blonde to brown hair and blue, green or brown eyes. This skin type sometimes burns, but otherwise goes brown quite easily. Type III is the most common skin type of races native to the UK.
  • TYPE IV skin is well adapted to the sun and rarely burns. Sometimes described as olive skin, it is naturally pale brown thanks to its high level of protective melanin. People of Mediterranean, middle Eastern or Central European origin tend to be Type IV
  • TYPE V skin has a great deal of natural sun protection. This skin type is naturally light brown, and hair is very dark brown or black. People of Asian or Far Eastern Origin tend to have this skin type.
  • TYPE VI skin is the best protected of all. It is typically dark brown to black, with black hair and brown eyes. It is well adapted to the sun and requires little protection from external sunscreens. People of African and Afro Caribbean origin tend to have this skin type.

Calculating your SPF

Selecting the correct SPF formula requires a conservative estimate of how long it would take for your skin to start burning if you were not wearing any sunscreen at all. The following chart will help.

Skin Type Burns SPF for 4 hours protection
Type I Immediately SPF 35+
Type II In 10-15 minutes SPF 25+
Type III In 20-30 minutes SPF 15+
Type IV In 45 minutes SPF 8-15
Type V In 1 hour SPF 6-12
Type VI In 1 hour 30 mins SPF 4-8

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