What is sun protection factor (SPF)? | Dr. Ankerstjerne

What is sun protection factor (SPF)?

What is the difference between factor 30 and factor 50? We have gathered everything you need to know about SPF here!

Most people know that one should protect themselves from the sun’s UV rays and that UV rays are harmful because it causes mole cancer and other skin cancer forms. Some also know that UV rays together with air pollution make up the two main causes of premature aging of the skin. But what exactly are UV rays? How do they affect the skin? Why are they harmful to us? And what is the solar factor? And where should the solar factor be used?

We have gathered all the information you need in two articles, one on solar factor and SPF (below) and one on UVA og UVB rays.


What is sun protection factor or SFP?

SPF stands for Sun Protection Factor or solar factor. SPF is only a measure of how much UVB rays one tolerates before becoming red in the skin. Many people are therefore not aware that the sun factor gives little protection against premature aging of the skin, which is mainly due to UVA rays.

How does UVB  rays affect the epidermis?

It is in the epidermis you have pigment cells that produce pigment (melanin) that gives color to the moles and the tan you get from sun exposure. This is why epidermal cancer and other skin cancers develop in the epidermis. It is also here that you get sunburned, which in itself is the signal to the pigment cells to produce more pigment. Pigment is one of the structures that absorbs UV rays without causing significant damage to the skin. Pigment is therefore the skin’s own protection against UV rays. The protection does not come completely free because it causes oxidative stress that eats the skin’s antioxidant stock. The most problematic with UVB rays is that they unfortunately largely hit the DNA in the cells. This can, via processes in the cell, cause mutations and in some cases give cells that can eventually develop into cancer cells. Read more about the difference between UVA and UVB rays here.

What is the difference between factor 30 and factor 50?

SPF is only a measure of protection against UVB rays. The number that follows SPF is a measure of whether the product provides high or low sun protection. SPF30 and SPF 50 are the terms used when talking about high solar factor. Many, however, have a completely wrong perception of the protective effect of an increase in solar factor. SPF50 sounds a lot more than SPF30. This is because the sun factor is a mathematical ratio. With increasing solar factor, exponentially decreasing marginal protective effect is seen. The truth is that SPF 30 filters out 97% of the UVB rays, while the SPF 50 filters out 98%. This is a minimal increase in UV protection that can give the consumer a false sense of security. Most often, other factors such as sweating, uneven application will have much more to say than choosing SPF 30 or SPF50.

​Did you know?

  • UVA rays cause premature aging of the skin.

  • UVB rays cause sunburn, skin cancer, and pigment damage, but are less important than UVA rays compared to premature skin aging.

  • SPF only says something about protection against UVB rays.

  • The SPF30 filters out 97% of the UVB rays while the SPF50 filters out 98%. Other factors such as uneven application and sweating are more common than using SPF30 or SPF50.

  • The side windows in cars filter out almost 100% of the UVB rays, but only approx. 20% of the UVA rays. It is therefore important to protect against UVA rays also in the car, to avoid premature skin aging!

URBAN PROTECTION daycream has both high solar factor and UVA protection – wide spectrum UV protection!

  • SPF30 + UVA
  • Broad-spectrum UV protection
  • 24 % reduction in length of wrinkles
  • Increased skin firmness and elasticity
  • Protection against air pollution mediated skindamage