Why is it important to protect our skin from UV rays?

While in Europe we like to sunbathe, in Asia it's considered to be harmful. Why?

Sun parasols are very popular in Asia.

What are UV rays and what influence they have on our skin?
Sun rays have been divided into few ranges according to their influence on humans. Surface of the Earth is reached by ultraviolet rays in range from 280 to 400 nanometres. There are three kinds of UV rays:

• UVC - 200-280nm - this kind of rays is almost completely absorbed by ozone sphere, so it doesn't reach surface of the Earth. This kind of rays are highly harmful - they may be used in laboratories or hospitals to sterilise surfaces.
• UVB - 280-320nm - represents 5% of rays reaching surface of the Earth and can't penetrate throughout clouds and glass, however it penetrates epidermis. UVB rays are responsible for sunbathing effects and also for sunburns, allergic reactions and skin cancers.
• UVA - 320-400nm - represents 95% of rays reaching surface of the Earth and it's present all year round, including winter. There rays penetrate throughout clouds, glass and epidermis and they are very tricky, as they don't cause any pain (so we don't sunburn with them). UVA rays are responsible for creating free radicals, that in long terms can provoke changes in cells, like photoaging, sun intolerance, pigmentation or even skin cancers.

Photo posted in New England Journal of Medicine showing negative effects of one-sided UV rays exposure after 30 years of driving truck.

So Asians are right hiding from sun ;) However we are not able to completely disable UV rays, how should we then protect our skin from it?

SPF and PA filters
SPF stand for "sun protection factor" and it's used to state protection level from UVB rays in suncare cosmetics. Factor is scaled from 2 to 50, however recently we may come across factors higher that 50. The SPF is calculated by comparing the amount of time needed to burn the skin that is protected to unprotected skin. For example: person who would normally get sunburned after 10 minutes of sunbathing, using SPF10 would get burned in ten times longer period of time, so after approx. 100hours if sunbathing with SPF (in constant UV). Cosmetics with SPF15 should stop 93% UVB, SPF30 - 97%. However we should remember that SPF filters are working only for two hours after application - after that time we should reapply them.

PA filters are protecting from UVA rays and have only very general, three levels scale: PA+, PA++ and PA+++. More pluses = more protection.
Filter protecting from UVA rays can be also marked with symbols IPD or PPD.

Unfortunately a lot of cosmetics still have only SPF filters, which don't offer our skin full protection. So far all the BB Creams I came across and tested had both filters.

Mineral and chemical filters 
Mineral filters, known also as a physical filters are compounds, that create physical barrier on our skin, reflecting or dispersing UV rays. Their molecules are big enough to not be able to penetrate epidermis, so they stay on the top of our skin, blocking UVB rays and some UVA rays. There are two compounds qualifying as a mineral filters: Titanium dioxide and Zinc oxide.

Pros of mineral filters:
+ well tolerated by skin, very rarely causing allergies
+ effective immediately after application
+ photostable - they don't loose their properties under influence of UV rays, oxidation or time
+ they don't accumulate in our system

Cons of mineral filters:
- on their own they are not able to provide us high protection against UV rays
- they may require often re-application (especially after swimming or activities causing intensive sweating)
- they may whiten skin or clog pores

Chemical filters are substances, that are penetrating epidermis, absorbing UV rays and converting them into harmless heat.

Pros of chemical filters:
+ highly effective
+ invisible on skin
+ non-greasy

Cons of chemical filters:
- less photostable than mineral filters
- may cause irritation
- not effective straight after application - we need to wait 20-30 minutes before they start working
- they may accumulate in our system

The less stabile filter, which is better to be avoided is oxybenozone (or Benzophenone - 3, Benzophenone - 4), trading names Eusolex 4360, Escalol 567, KAHSCREEN BZ-3.

In generall the most effective sun screens would be mixers of mineral and chemical filters, like Mexoryl SX, Mexoryl XL, Tinosorb S, Tinosorb M.
 
Stay safe
Even using the best filters we should still remember about rules of safe sunbathing. It's best to sunbathe in movement and reduce our exposition to sun between 12pm and 3pm. If you are on holiday and planing to sunbathe everyday it's best to divide it in steps, starting from just 10-15 minutes the first day and then extending the sunbathing time every next day. Also bear in mind that near water (and it the water) the sun is exposure is doubled up, as UV rays are reflected by water.

The most common mistake is using UV protection only in the summer - UV rays are dangerous to our skin through the whole year, regardless of the temperature and clouds. If you want healthy, young looking skin you should remember about UV filters all year round. If you can't be bothered with lotions/sprays with filters it worth looking for cosmetics you use everyday anyway with filters. In European market is very easy to find day cream with UV filter, on Asian market almost every BB cream contains SPF. Unfortunately, to provide our skin maximal protection we should reapply filter every 2-3 hours, so the easy and simple solutions are powders/pacts with SPF.

Skin Food's powder pact with high filters SPF50 PA+++.