Whilst getting sunburnt is a very bad thing ,
It is probably a good idea to know what is going on with suncreams of various types.
Whenever you see factor 15 for example, that means the UVB light is cut down to 1/15 of its original intensity. I does NOT mean that all ultraviolet radiation is cut down to 1/15 , there are other longer wavelength rays in sunlight , known as UVA . UVA does not cause sunburn, however it is a deeply penetrating form of sunlight , associated with skin aging etc. Keeping out for long periods in intense sunlight , like Greece, southern Spain etc is not really a good idea, even if you have factor 50 , on the skin. You may not burn , but the UVA is still there, penetrating the skin.
Some sunscreens block some of the UVA ,but not all of it. ( UVA+UVB type sunscreen. ) . The " Factor " levels only refers to UVB
UVB is only about 1 or 2 % of sunlight , depending upon where you are in the world, and depending on the height of the sun in the sky.
The lower the sun, the less UVB ( burning rays ) but UVA is still present. So time of day is a factor.
Human skin uses UVB rays to manufacture Vitamin D , which is an essential nutrient for us. UVA cannot manufacture Vitamin D.
There are many types of sunscreen, with varying formulations, anything factor 15 or above will essentially stop Vit D production, (97% of UVB ) whilst it is on the skin. Factor 30 , will block 98% , Factor 50, 99% or more. IF you are paying a lot extra for factor 50 , it does not make much difference, as you can see. The amount of UVA let through depends upon the formulation of the sunscreen.
Please note : there has never been a long term trial upon the effect of sunscreen chemicals on human health. Sunscreens are classed as cosmetics , and do not need the thorough investigation that drugs have in order to be sold. Vitamin D is a steriod hormone , essential for human health. If a company were to try and sell a drug which diminished the production of an essential human hormone by 97% , it would be tested rigourously.
That's just a few facts about sunscreens that are not commonly considered ,hope they are useful !
I am not anti-sun , I am pro knowledge , about what sunlight is , how it affects us , what is best for health without being encouraged to use expensive products by companies that say that we need their products to stay healthy. We actually need some sun to remain healthy.