Sun protection: breaking down SPF, UVA and UVB

Sun protection: breaking down SPF, UVA and UVB

It amazes me that consumers are so focused on the SPF rating on their sunscreen. SPF is only half of the solution to sun protection. SPF measures burning rays or UVB rays only. SPF is a mathematical equation indicating how long you can stay out in the sun without turning red!

SPF does not measure your sun protection from UVA rays.

Ultraviolet (UV) radiation is part of the invisible light spectrum that reaches earth from the sun. These wavelengths are then classified into three categories – UVA, UVB and UVC. UVA and UVB protection is vital. Sunscreens shielding us from the damage from both these rays is referred to as ‘broad spectrum’.

So, what is the difference between UVA and UVB?

UVA is primarily responsible for skin Ageing (A=Ageing) as it breaks down the collagen in our skin. UVA rays are far more serious in my opinion. These rays penetrate deeper into the skin. But more importantly UVA shuts down the skins immune surveillance system so it is unable to fight damage by the sun. Many skin cancers and potentially fatal melanoma can be caused by UVA damage.

UVA rays:
  • Are the longest wavelength rays and therefore penetrate the deepest into the skin (the dermis)
  • Comprise 95% of the sun’s rays reaching earth
  • Are responsible for ageing (due to collagen destruction)
  • Can cause skin cancer (benign and malignant)
  • Suppresses the immune system of the skin making us more prone to skin cancer
  • Can penetrate glass
  • Are constant in intensity throughout the day and seasons.
UVB rays
  • These are shorter rays and can only penetrate the surface layer of the skin (epidermis)
  • Causes burning of the skin
  • Can also cause cancer
  • More intense between 11am and 2pm
UVC rays
  • Thankfully these lethal rays are absorbed by the ozone layer and do not reach the earth’s surface provided we preserve the ozone layer!
Broad spectrum protection

I am also concerned that consumers are not aware of the difference between physical and chemical sunscreens. 

Chemical sunscreens absorb into the skin and act by absorbing UV light. They are later broken down in the body and carried in the bloodstream where the by products may be stored in the body. There has been evidence that many chemical sunscreens may be harmful and have been linked to hormonal imbalances.

Physical sunscreens sit on top of the skin. They are not absorbed and they provide a protective barrier to UV light.

Any sunscreen is better than none at all but given the choice, my advice is to opt for physical sunscreen in the form of zinc oxide such as ÜberZinc – a natural mineral that blocks harmful UVA and UVB rays.

Next time you purchase sunscreen, look for the terms ‘UVA/UVB protection’, or ‘broad spectrum protection’. Always check the label and ingredient list before you make a purchase.