|
Are you confused about sunscreens and all the terminology surrounding them? There are a lot of misconceptions about SPF factors and sunscreen ingredients. So, we'll try to help dispell the myths for you.
In theory, the SPF is a multiplier that can be applied to the time taken to burn. For example, someone who would burn after 10 minutes in the sun would expect to burn after 100 minutes if protected by a sunscreen with SPF 10, 150 minutes if protected by a sunscreen with SPF 15, 200 minutes if protected by a sunscreen with SPF 20, etc. There are several misconceptions with these numbers and they often mislead consumers into thinking they are getting more protection then they are.
Protection from a particular sunscreen actually depends on several factors such as:
1) Skin type of the user.
2) Amount applied and frequency of re-application.
3) Activities in which one engages (for example, swimming leads to a loss of sunscreen from the skin).
4) Time of day and season.
5) Percentage of UV reflected or scattered by the environment, for example snow, sand or water.
6) Amount of sunscreen the skin has absorbed.
7) Altitude.
8) Proximity to the Equator
A sunscreen with an SPF of x blocks a proportion (x-1)/x of UVB:
Sun Protection Factor and Proportion of UVB blocked
SPF 10 = 90.0%
SPF 15 = 93.3%
SPF 20 = 95.0%
SPF 30 = 96.7%
SPF 60 = 97.0%
As you can see, the extra UVB rays blocked by sunscreens with an SPF over 30 is very minimal and you can NEVER achieve 100% sun protection unless you stay out of the sun - thus, the term sunblock was banned from use by the FDA.
In order to achieve higher SPF levels, manufactures need to use more active ingredients, and once the SPF is over 30, the extra protection may not be worth the extra chemicals.
There are two types of ingredients used in sunscreens -
1) chemical blockers - absorb UV radiation, lowering energy levels, release energy as heat, may irritate the skin at higher concentrations (benzophenone, avobenzone, octyl methoxycinnamate)
2) physical blockers - reflect or scatter energy rays, physical block the UV radiation, non-irritating to the skin (titanium dioxide, zinc oxide)
Please note that the SPF system only measures the degree of protection from UVB exposure (UVB rays are the primary cause of sunburns, affect the outer layer of skin, and are associated with skin cancer). There isn't currently a rating system that measures the degree of protection from UVA exposure (UVA rays contribute to age-related changes in the skin and are also associated with skin cancer). I recommend reading the list of ingredients in a sunscreen to see if it has "broad-spectrum" (UVA and UVB) coverage. A good broad-spectrum sunscreen should contain avobenzone, titanium dioxide, or zinc oxide for significant UVA protection.
Hopefully, we've been able to shed some light on sunscreens for you. |
